diff --git a/PROGRESS.md b/PROGRESS.md
index 551cccb..be08160 100644
--- a/PROGRESS.md
+++ b/PROGRESS.md
@@ -12,7 +12,7 @@
 | 0.1 | ✅ done | 2026-07-23 | codebase-vs-requirements.md neu geschrieben, security-review-phase2.md Resolution Summary, architecture.md Implementation Status, MASTER-PLAN.md + PROGRESS.md erstellt |
 | 0.2 | ✅ done | 2026-07-23 | lucide-react installieren + Icons migrieren |
 | 0.3 | ✅ done | 2026-07-23 | date-fns installieren + Datum-Formatierung |
-| 0.4 | ⬜ pending | | hooks.ts aufteilen |
+| 0.4 | ✅ done | 2026-07-23 | hooks.ts aufteilen — 1298 Zeilen → 12 Module + Re-Export-Hub |
 | 0.5 | ⬜ pending | | Store-Verzeichnis konsolidieren |
 | 0.6 | ⬜ pending | | Frontend-Bestandsanalyse als Dokument speichern |
 | 0.7 | ⬜ pending | | UI-Design-Richtlinien erstellen |
diff --git a/frontend/src/api/attachments.ts b/frontend/src/api/attachments.ts
new file mode 100644
index 0000000..e401e0a
--- /dev/null
+++ b/frontend/src/api/attachments.ts
@@ -0,0 +1,123 @@
+/**
+ * Attachment and address hooks.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete, apiClient } from './client';
+
+export interface Attachment {
+  id: string;
+  entity_type: string;
+  entity_id: string;
+  filename: string;
+  file_path: string;
+  mime_type: string;
+  file_size: number;
+  uploaded_by?: string | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface Address {
+  id: string;
+  entity_type: string;
+  entity_id: string;
+  label: string;
+  address_type: string;
+  street: string | null;
+  street_number: string | null;
+  city: string | null;
+  zip: string | null;
+  state: string | null;
+  country: string | null;
+  is_default: boolean;
+  created_at?: string;
+  updated_at?: string;
+}
+
+// Attachments
+export function useAttachments(entityType?: string, entityId?: string) {
+  return useQuery({
+    queryKey: ['attachments', entityType, entityId],
+    queryFn: () => {
+      const params = new URLSearchParams();
+      if (entityType) params.set('entity_type', entityType);
+      if (entityId) params.set('entity_id', entityId);
+      return apiGet<{ items: Attachment[]; total: number }>(`/attachments?${params.toString()}`);
+    },
+    enabled: !!entityType && !!entityId,
+  });
+}
+
+export function useUploadAttachment() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: async ({ file, entityType, entityId }: { file: File; entityType: string; entityId: string }) => {
+      const formData = new FormData();
+      formData.append('file', file);
+      formData.append('entity_type', entityType);
+      formData.append('entity_id', entityId);
+      const response = await apiClient.post('/attachments', formData, {
+        headers: { 'Content-Type': 'multipart/form-data' },
+      });
+      return response.data;
+    },
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['attachments'] });
+    },
+  });
+}
+
+export function useDeleteAttachment() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/attachments/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['attachments'] });
+    },
+  });
+}
+
+// Addresses
+export function useAddresses(entityType?: string, entityId?: string) {
+  return useQuery({
+    queryKey: ['addresses', entityType, entityId],
+    queryFn: () =>
+      apiGet<{ items: Address[]; total: number }>(
+        `/addresses?entity_type=${entityType}&entity_id=${entityId}`
+      ),
+    enabled: !!entityType && !!entityId,
+  });
+}
+
+export function useCreateAddress() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<Address> & { entity_type: string; entity_id: string }) =>
+      apiPost('/addresses', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['addresses'] });
+    },
+  });
+}
+
+export function useUpdateAddress() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<Address> }) =>
+      apiPatch(`/addresses/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['addresses'] });
+    },
+  });
+}
+
+export function useDeleteAddress() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/addresses/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['addresses'] });
+    },
+  });
+}
diff --git a/frontend/src/api/audit.ts b/frontend/src/api/audit.ts
new file mode 100644
index 0000000..cf8ec4b
--- /dev/null
+++ b/frontend/src/api/audit.ts
@@ -0,0 +1,32 @@
+/**
+ * Audit log hooks.
+ */
+
+import { useQuery } from '@tanstack/react-query';
+import { apiGet } from './client';
+import { PaginatedResponse } from './types';
+
+export interface AuditLogEntry {
+  id: string;
+  timestamp: string;
+  user: string;
+  action: string;
+  entity: string;
+  entity_id?: string;
+  details?: string;
+}
+
+export function useAuditLog(page = 1, pageSize = 25, filters?: { user?: string; action?: string; entity?: string; dateFrom?: string; dateTo?: string }) {
+  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
+  if (filters?.user) params.set('user', filters.user);
+  if (filters?.action) params.set('action', filters.action);
+  if (filters?.entity) params.set('entity', filters.entity);
+  if (filters?.dateFrom) params.set('date_from', filters.dateFrom);
+  if (filters?.dateTo) params.set('date_to', filters.dateTo);
+  return useQuery({
+    queryKey: ['auditLog', page, pageSize, filters],
+    queryFn: () =>
+      apiGet<PaginatedResponse<AuditLogEntry>>(`/audit-log?${params.toString()}`),
+    retry: false,
+  });
+}
diff --git a/frontend/src/api/auth.ts b/frontend/src/api/auth.ts
new file mode 100644
index 0000000..eec4f03
--- /dev/null
+++ b/frontend/src/api/auth.ts
@@ -0,0 +1,95 @@
+/**
+ * Authentication hooks: login, logout, current user, password reset, tenant switching.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiPost, apiGet, setCsrfToken } from './client';
+import { useAuthStore } from '@/store/authStore';
+
+export interface LoginPayload {
+  email: string;
+  password: string;
+}
+
+export interface PasswordResetRequestPayload {
+  email: string;
+}
+
+export interface PasswordResetConfirmPayload {
+  token: string;
+  password: string;
+}
+
+export function useLogin() {
+  const { setUser, setError } = useAuthStore();
+  return useMutation({
+    mutationFn: (payload: LoginPayload) =>
+      apiPost('/auth/login', payload),
+    onSuccess: (data: any) => {
+      setUser(data.user || data);
+      setError(null);
+      // Store CSRF token for subsequent unsafe requests
+      if (data.csrf_token) {
+        setCsrfToken(data.csrf_token);
+      }
+    },
+    onError: (error: any) => {
+      setError(error.message || 'Login failed');
+    },
+  });
+}
+
+export function useLogout() {
+  const { logout } = useAuthStore();
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: () => apiPost('/auth/logout'),
+    onSettled: () => {
+      logout();
+      setCsrfToken(null);
+      queryClient.clear();
+    },
+  });
+}
+
+export function useCurrentUser() {
+  const { setUser, setAuthenticated } = useAuthStore();
+  return useQuery({
+    queryKey: ['currentUser'],
+    queryFn: async () => {
+      const data = await apiGet<any>('/auth/me');
+      setUser(data.user || data);
+      setAuthenticated(true);
+      return data;
+    },
+    retry: false,
+    staleTime: 5 * 60 * 1000,
+  });
+}
+
+export function usePasswordResetRequest() {
+  return useMutation({
+    mutationFn: (payload: PasswordResetRequestPayload) =>
+      apiPost('/auth/password-reset/request', payload),
+  });
+}
+
+export function usePasswordResetConfirm() {
+  return useMutation({
+    mutationFn: (payload: PasswordResetConfirmPayload) =>
+      apiPost('/auth/password-reset/confirm', payload),
+  });
+}
+
+export function useSwitchTenant() {
+  const { setTenant } = useAuthStore();
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (tenantId: string) =>
+      apiPost('/auth/switch-tenant', { tenant_id: tenantId }),
+    onSuccess: (data: any) => {
+      setTenant(data.tenant || data);
+      queryClient.invalidateQueries();
+    },
+  });
+}
diff --git a/frontend/src/api/contacts.ts b/frontend/src/api/contacts.ts
new file mode 100644
index 0000000..c3182ba
--- /dev/null
+++ b/frontend/src/api/contacts.ts
@@ -0,0 +1,111 @@
+/**
+ * Contact CRUD hooks (legacy contact model — not unified contacts).
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete, apiPut } from './client';
+import { PaginatedResponse, Contact, ContactDetail } from './types';
+import { ContactFolder } from './contactFolders';
+
+export function useContacts(page = 1, pageSize = 25, search?: string) {
+  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
+  if (search) params.set('search', search);
+  return useQuery({
+    queryKey: ['contacts', page, pageSize, search],
+    queryFn: () =>
+      apiGet<PaginatedResponse<Contact>>(`/contacts?${params.toString()}`),
+  });
+}
+
+export function useContact(id?: string) {
+  return useQuery({
+    queryKey: ['contacts', id],
+    queryFn: () => apiGet<ContactDetail>(`/contacts/${id}`),
+    enabled: !!id,
+  });
+}
+
+export function useCreateContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<Contact> & { company_ids?: string[] }) =>
+      apiPost('/contacts', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contacts'] });
+    },
+  });
+}
+
+export function useUpdateContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<Contact> & { company_ids?: string[] } }) =>
+      apiPatch(`/contacts/${id}`, data),
+    onSuccess: (_data, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['contacts'] });
+      queryClient.invalidateQueries({ queryKey: ['contacts', variables.id] });
+    },
+  });
+}
+
+export function useDeleteContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/contacts/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contacts'] });
+    },
+  });
+}
+
+// ── Contact Folders ──
+
+export function useContactFolders() {
+  return useQuery({
+    queryKey: ['contactFolders'],
+    queryFn: () => apiGet<ContactFolder[]>('/contact-folders'),
+  });
+}
+
+export function useCreateContactFolder() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: { name: string; parent_id?: string }) => apiPost('/contact-folders', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
+    },
+  });
+}
+
+export function useUpdateContactFolder() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: { name?: string; parent_id?: string | null; sort_order?: number } }) =>
+      apiPut(`/contact-folders/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
+    },
+  });
+}
+
+export function useDeleteContactFolder() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/contact-folders/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
+    },
+  });
+}
+
+export function useMoveContactToFolder() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ contactId, folderId }: { contactId: string; folderId: string | null }) =>
+      apiPut(`/contact-folders/contacts/${contactId}/move`, { folder_id: folderId }),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
+    },
+  });
+}
diff --git a/frontend/src/api/groups.ts b/frontend/src/api/groups.ts
new file mode 100644
index 0000000..f5a87d9
--- /dev/null
+++ b/frontend/src/api/groups.ts
@@ -0,0 +1,99 @@
+/**
+ * Group and group member hooks.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete } from './client';
+
+export interface Group {
+  id: string;
+  name: string;
+  description: string | null;
+  permissions: Record<string, any>;
+  denied_permissions: string[];
+  field_permissions: Record<string, any>;
+  permission_version: number;
+}
+
+export interface GroupMember {
+  user_id: string;
+  email: string;
+  name: string;
+  is_active: boolean;
+}
+
+export function useGroups() {
+  return useQuery({
+    queryKey: ['groups'],
+    queryFn: () => apiGet<{ items: Group[] }>('/groups'),
+  });
+}
+
+export function useCreateGroup() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<Group>) => apiPost('/groups', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['groups'] });
+    },
+  });
+}
+
+export function useUpdateGroup() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<Group> }) =>
+      apiPatch(`/groups/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['groups'] });
+    },
+  });
+}
+
+export function useDeleteGroup() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/groups/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['groups'] });
+    },
+  });
+}
+
+export function useGroupMembers(groupId: string | null) {
+  return useQuery({
+    queryKey: ['groupMembers', groupId],
+    queryFn: () => apiGet<{ items: GroupMember[] }>(`/groups/${groupId}/members`),
+    enabled: !!groupId,
+  });
+}
+
+export function useAddGroupMember() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ groupId, userId }: { groupId: string; userId: string }) =>
+      apiPost(`/groups/${groupId}/members`, { user_id: userId }),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['groupMembers'] });
+    },
+  });
+}
+
+export function useRemoveGroupMember() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ groupId, userId }: { groupId: string; userId: string }) =>
+      apiDelete(`/groups/${groupId}/members/${userId}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['groupMembers'] });
+    },
+  });
+}
+
+export function useUserGroups(userId: string | null) {
+  return useQuery({
+    queryKey: ['userGroups', userId],
+    queryFn: () => apiGet<{ items: Group[] }>(`/groups/user/${userId}`),
+    enabled: !!userId,
+  });
+}
diff --git a/frontend/src/api/hooks.ts b/frontend/src/api/hooks.ts
index 5b6367f..5b54fd1 100644
--- a/frontend/src/api/hooks.ts
+++ b/frontend/src/api/hooks.ts
@@ -1,70 +1,31 @@
+/**
+ * hooks.ts — Re-Export Hub
+ *
+ * This file re-exports all hooks from their dedicated modules so that
+ * existing imports `from '@/api/hooks'` continue to work without change.
+ *
+ * Company hooks remain inline here — they will be removed in Phase 1.
+ */
+
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
-import { apiPost, apiGet, apiPatch, apiPut, apiDelete, apiClient, setCsrfToken } from './client';
-import { useAuthStore } from '@/store/authStore';
+import { apiGet, apiPost, apiPatch, apiDelete, apiClient } from './client';
+import { PaginatedResponse, Company, CompanyDetail } from './types';
 
-export interface LoginPayload {
-  email: string;
-  password: string;
-}
+// ── Re-exports from dedicated modules ──
+export * from './types';
+export * from './auth';
+export * from './users';
+export * from './contacts';
+export * from './roles';
+export * from './groups';
+export * from './audit';
+export * from './notifications';
+export * from './plugins';
+export * from './settings';
+export * from './attachments';
+export * from './unifiedContacts';
 
-export interface PasswordResetRequestPayload {
-  email: string;
-}
-
-export interface PasswordResetConfirmPayload {
-  token: string;
-  password: string;
-}
-
-export interface PaginatedResponse<T> {
-  items: T[];
-  total: number;
-  page: number;
-  page_size: number;
-}
-
-export interface Company {
-  id: string;
-  name: string;
-  account_number?: string | null;
-  industry?: string | null;
-  phone?: string | null;
-  email?: string | null;
-  website?: string | null;
-  description?: string | null;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface CompanyDetail extends Company {
-  contacts?: Contact[];
-}
-
-export interface Contact {
-  id: string;
-  first_name: string;
-  last_name: string;
-  email: string;
-  phone?: string | null;
-  position?: string | null;
-  company_ids?: string[];
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface ContactDetail extends Contact {
-  companies?: Company[];
-}
-
-export interface AuditLogEntry {
-  id: string;
-  timestamp: string;
-  user: string;
-  action: string;
-  entity: string;
-  entity_id?: string;
-  details?: string;
-}
+// ── Search hook (uses dynamic import, kept inline) ──
 
 export interface SearchResult {
   type: 'company' | 'contact' | 'mail' | 'file' | 'event';
@@ -74,164 +35,21 @@ export interface SearchResult {
   url: string;
 }
 
-export interface Role {
-  id: string;
-  name: string;
-  permissions: Record<string, any>;
-  field_permissions?: Record<string, any>;
-}
-
-export interface PermissionItem {
-  key: string;
-  label: string;
-  category: string;
-  plugin_name?: string;
-}
-
-export interface FieldDefinition {
-  module: string;
-  field: string;
-  label: string;
-  sensitivity: string;
-}
-
-export interface PermissionsResponse {
-  system: PermissionItem[];
-  plugins: PermissionItem[];
-  all: PermissionItem[];
-  field_definitions?: FieldDefinition[];
-}
-
-export interface Plugin {
-  name: string;
-  display_name?: string;
-  description?: string;
-  version?: string;
-  status: 'discovered' | 'installed' | 'active' | 'inactive';
-  installed?: boolean;
-  active?: boolean;
-}
-
-export function useLogin() {
-  const { setUser, setError } = useAuthStore();
-  return useMutation({
-    mutationFn: (payload: LoginPayload) =>
-      apiPost('/auth/login', payload),
-    onSuccess: (data: any) => {
-      setUser(data.user || data);
-      setError(null);
-      // Store CSRF token for subsequent unsafe requests
-      if (data.csrf_token) {
-        setCsrfToken(data.csrf_token);
-      }
-    },
-    onError: (error: any) => {
-      setError(error.message || 'Login failed');
-    },
-  });
-}
-
-export function useLogout() {
-  const { logout } = useAuthStore();
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: () => apiPost('/auth/logout'),
-    onSettled: () => {
-      logout();
-      setCsrfToken(null);
-      queryClient.clear();
-    },
-  });
-}
-
-export function useCurrentUser() {
-  const { setUser, setAuthenticated } = useAuthStore();
+export function useGlobalSearch(query: string, entityTypes?: string[]) {
   return useQuery({
-    queryKey: ['currentUser'],
-    queryFn: async () => {
-      const data = await apiGet<any>('/auth/me');
-      setUser(data.user || data);
-      setAuthenticated(true);
-      return data;
+    queryKey: ['globalSearch', query, entityTypes],
+    queryFn: async (): Promise<SearchResult[]> => {
+      if (!query.trim()) return [];
+      const { search } = await import('@/api/search');
+      const response = await search(query, entityTypes, 20);
+      return response.results || [];
     },
-    retry: false,
-    staleTime: 5 * 60 * 1000,
+    enabled: query.trim().length > 0,
+    staleTime: 30 * 1000,
   });
 }
 
-export function usePasswordResetRequest() {
-  return useMutation({
-    mutationFn: (payload: PasswordResetRequestPayload) =>
-      apiPost('/auth/password-reset/request', payload),
-  });
-}
-
-export function usePasswordResetConfirm() {
-  return useMutation({
-    mutationFn: (payload: PasswordResetConfirmPayload) =>
-      apiPost('/auth/password-reset/confirm', payload),
-  });
-}
-
-export function useSwitchTenant() {
-  const { setTenant } = useAuthStore();
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (tenantId: string) =>
-      apiPost('/auth/switch-tenant', { tenant_id: tenantId }),
-    onSuccess: (data: any) => {
-      setTenant(data.tenant || data);
-      queryClient.invalidateQueries();
-    },
-  });
-}
-
-export function useUsers(page = 1, pageSize = 25) {
-  return useQuery({
-    queryKey: ['users', page, pageSize],
-    queryFn: () =>
-      apiGet<PaginatedResponse<any>>(`/users?page=${page}&page_size=${pageSize}`),
-  });
-}
-
-export function useUser(id?: string) {
-  return useQuery({
-    queryKey: ['users', id],
-    queryFn: () => apiGet<any>(`/users/${id}`),
-    enabled: !!id,
-  });
-}
-
-export function useCreateUser() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: any) => apiPost('/users', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['users'] });
-    },
-  });
-}
-
-export function useUpdateUser() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: any }) =>
-      apiPatch(`/users/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['users'] });
-    },
-  });
-}
-
-export function useDeleteUser() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/users/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['users'] });
-    },
-  });
-}
+// ── Company hooks (will be removed in Phase 1) ──
 
 export function useCompanies(page = 1, pageSize = 25, search?: string, industry?: string, sortBy?: string, sortOrder?: string) {
   const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
@@ -316,983 +134,3 @@ export function useCompanyImport() {
     },
   });
 }
-
-export function useContacts(page = 1, pageSize = 25, search?: string) {
-  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
-  if (search) params.set('search', search);
-  return useQuery({
-    queryKey: ['contacts', page, pageSize, search],
-    queryFn: () =>
-      apiGet<PaginatedResponse<Contact>>(`/contacts?${params.toString()}`),
-  });
-}
-
-export function useContact(id?: string) {
-  return useQuery({
-    queryKey: ['contacts', id],
-    queryFn: () => apiGet<ContactDetail>(`/contacts/${id}`),
-    enabled: !!id,
-  });
-}
-
-export function useCreateContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<Contact> & { company_ids?: string[] }) =>
-      apiPost('/contacts', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contacts'] });
-    },
-  });
-}
-
-export function useUpdateContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<Contact> & { company_ids?: string[] } }) =>
-      apiPatch(`/contacts/${id}`, data),
-    onSuccess: (_data, variables) => {
-      queryClient.invalidateQueries({ queryKey: ['contacts'] });
-      queryClient.invalidateQueries({ queryKey: ['contacts', variables.id] });
-    },
-  });
-}
-
-export function useDeleteContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/contacts/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contacts'] });
-    },
-  });
-}
-
-export function useAuditLog(page = 1, pageSize = 25, filters?: { user?: string; action?: string; entity?: string; dateFrom?: string; dateTo?: string }) {
-  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
-  if (filters?.user) params.set('user', filters.user);
-  if (filters?.action) params.set('action', filters.action);
-  if (filters?.entity) params.set('entity', filters.entity);
-  if (filters?.dateFrom) params.set('date_from', filters.dateFrom);
-  if (filters?.dateTo) params.set('date_to', filters.dateTo);
-  return useQuery({
-    queryKey: ['auditLog', page, pageSize, filters],
-    queryFn: () =>
-      apiGet<PaginatedResponse<AuditLogEntry>>(`/audit-log?${params.toString()}`),
-    retry: false,
-  });
-}
-
-export function useGlobalSearch(query: string, entityTypes?: string[]) {
-  return useQuery({
-    queryKey: ['globalSearch', query, entityTypes],
-    queryFn: async (): Promise<SearchResult[]> => {
-      if (!query.trim()) return [];
-      const { search } = await import('@/api/search');
-      const response = await search(query, entityTypes, 20);
-      return response.results || [];
-    },
-    enabled: query.trim().length > 0,
-    staleTime: 30 * 1000,
-  });
-}
-
-export function useNotifications() {
-  return useQuery({
-    queryKey: ['notifications'],
-    queryFn: () => apiGet<PaginatedResponse<any>>('/notifications'),
-  });
-}
-
-export function useUnreadNotificationCount() {
-  return useQuery({
-    queryKey: ['notifications', 'unread-count'],
-    queryFn: () => apiGet<number>('/notifications/unread-count'),
-  });
-}
-
-export function useMarkNotificationRead() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiPatch(`/notifications/${id}/read`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['notifications'] });
-    },
-  });
-}
-
-export function useDeleteNotification() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/notifications/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['notifications'] });
-    },
-  });
-}
-
-export interface NotificationTypeItem {
-  type_key: string;
-  plugin_name: string;
-  category: string;
-  label: string;
-  description: string | null;
-  is_enabled_by_default: boolean;
-  is_enabled: boolean;
-}
-
-export function useNotificationTypes() {
-  return useQuery({
-    queryKey: ['notification-types'],
-    queryFn: () => apiGet<{ items: NotificationTypeItem[] }>('/notifications/types'),
-  });
-}
-
-export function useNotificationPreferences() {
-  return useQuery({
-    queryKey: ['notification-preferences'],
-    queryFn: () => apiGet<{ items: { type_key: string; is_enabled: boolean }[] }>('/notifications/preferences'),
-  });
-}
-
-export function useUpdateNotificationPreference() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ typeKey, isEnabled }: { typeKey: string; isEnabled: boolean }) =>
-      apiPatch(`/notifications/preferences/${typeKey}`, { is_enabled: isEnabled }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['notification-preferences'] });
-      queryClient.invalidateQueries({ queryKey: ['notification-types'] });
-    },
-  });
-}
-
-export function usePlugins() {
-  return useQuery({
-    queryKey: ['plugins'],
-    queryFn: async () => {
-      const data = await apiGet<any>('/plugins');
-      return data;
-    },
-  });
-}
-
-export function useInstallPlugin() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (name: string) => apiPost(`/plugins/${name}/install`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['plugins'] });
-    },
-  });
-}
-
-export function useActivatePlugin() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (name: string) => apiPost(`/plugins/${name}/activate`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['plugins'] });
-    },
-  });
-}
-
-export function useDeactivatePlugin() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (name: string) => apiPost(`/plugins/${name}/deactivate`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['plugins'] });
-    },
-  });
-}
-
-export function useUninstallPlugin() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ name, removeData }: { name: string; removeData: boolean }) =>
-      apiDelete(`/plugins/${name}?remove_data=${removeData}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['plugins'] });
-    },
-  });
-}
-
-export function useRoles() {
-  return useQuery({
-    queryKey: ['roles'],
-    queryFn: async () => {
-      const data = await apiGet<any>('/roles');
-      return data;
-    },
-  });
-}
-
-export function usePermissions() {
-  return useQuery({
-    queryKey: ['permissions'],
-    queryFn: () => apiGet<PermissionsResponse>('/roles/permissions'),
-  });
-}
-
-export function useCreateRole() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: { name: string; permissions: Record<string, any>; field_permissions: Record<string, any> }) =>
-      apiPost('/roles', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['roles'] });
-    },
-  });
-}
-
-export function useUpdateRole() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: { name?: string; permissions?: Record<string, any>; field_permissions?: Record<string, any> } }) =>
-      apiPatch(`/roles/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['roles'] });
-    },
-  });
-}
-
-export function useDeleteRole() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/roles/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['roles'] });
-    },
-  });
-}
-
-// ════════════════════════════════════════════════════════════════════════════
-
-// ════════════════════════════════════════════════════════════════════════════
-// Unified Contact (Rentman-style) hooks
-// ════════════════════════════════════════════════════════════════════════════
-
-export interface ContactPerson {
-  id: string;
-  contact_id: string;
-  displayname: string;
-  firstname?: string | null;
-  middle_name?: string | null;
-  lastname?: string | null;
-  function?: string | null;
-  phone?: string | null;
-  mobilephone?: string | null;
-  email?: string | null;
-  street?: string | null;
-  number?: string | null;
-  postalcode?: string | null;
-  city?: string | null;
-  state?: string | null;
-  country?: string | null;
-  tags?: string | null;
-  custom?: Record<string, any> | null;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface UnifiedContact {
-  id: string;
-  type: 'company' | 'person';
-  displayname: string;
-  name?: string | null;
-  firstname?: string | null;
-  surname?: string | null;
-  surfix?: string | null;
-  ext_name_line?: string | null;
-  gender?: string | null;
-  code?: string | null;
-  accounting_code?: string | null;
-  vendor_accounting_code?: string | null;
-  // Mailing address
-  mailing_street?: string | null;
-  mailing_number?: string | null;
-  mailing_unit_number?: string | null;
-  mailing_district?: string | null;
-  mailing_extra_address_line?: string | null;
-  mailing_postalcode?: string | null;
-  mailing_city?: string | null;
-  mailing_state?: string | null;
-  mailing_country?: string | null;
-  // Visit address
-  visit_street?: string | null;
-  visit_number?: string | null;
-  visit_unit_number?: string | null;
-  visit_district?: string | null;
-  visit_extra_address_line?: string | null;
-  visit_postalcode?: string | null;
-  visit_city?: string | null;
-  visit_state?: string | null;
-  // Invoice address
-  invoice_street?: string | null;
-  invoice_number?: string | null;
-  invoice_unit_number?: string | null;
-  invoice_district?: string | null;
-  invoice_extra_address_line?: string | null;
-  invoice_postalcode?: string | null;
-  invoice_city?: string | null;
-  invoice_state?: string | null;
-  invoice_country?: string | null;
-  country?: string | null;
-  // Communication
-  phone_1?: string | null;
-  phone_2?: string | null;
-  email_1?: string | null;
-  email_2?: string | null;
-  website?: string | null;
-  // Financial
-  vat_code?: string | null;
-  fiscal_code?: string | null;
-  commerce_code?: string | null;
-  purchase_number?: string | null;
-  bic?: string | null;
-  bank_account?: string | null;
-  // Discounts
-  discount_crew: number;
-  discount_transport: number;
-  discount_rental: number;
-  discount_sale: number;
-  discount_subrent: number;
-  discount_total: number;
-  // Geo
-  latitude?: number | null;
-  longitude?: number | null;
-  // Notes
-  projectnote?: string | null;
-  projectnote_title?: string | null;
-  contact_warning?: string | null;
-  tags?: string | null;
-  image?: string | null;
-  custom?: Record<string, any> | null;
-  folder_id?: string | null;
-  default_person_id?: string | null;
-  admin_contactperson_id?: string | null;
-  contact_persons?: ContactPerson[];
-  created_at?: string;
-  updated_at?: string;
-}
-
-export function useUnifiedContacts(
-  page = 1,
-  pageSize = 25,
-  search?: string,
-  contactType?: string,
-  sortBy?: string,
-  sortOrder?: string,
-  folderId?: string,
-) {
-  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
-  if (search) params.set('search', search);
-  if (contactType) params.set('type', contactType);
-  if (sortBy) params.set('sort_by', sortBy);
-  if (sortOrder) params.set('sort_order', sortOrder);
-  if (folderId) params.set('folder_id', folderId);
-  return useQuery({
-    queryKey: ['unifiedContacts', page, pageSize, search, contactType, sortBy, sortOrder, folderId],
-    queryFn: () =>
-      apiGet<PaginatedResponse<UnifiedContact>>(`/contacts?${params.toString()}`),
-  });
-}
-
-export function useUnifiedContact(id?: string) {
-  return useQuery({
-    queryKey: ['unifiedContacts', id],
-    queryFn: () => apiGet<UnifiedContact & { contact_persons: ContactPerson[] }>(`/contacts/${id}`),
-    enabled: !!id,
-  });
-}
-
-export function useCreateUnifiedContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<UnifiedContact>) => apiPost('/contacts', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-    },
-  });
-}
-
-export function useUpdateUnifiedContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<UnifiedContact> }) =>
-      apiPut(`/contacts/${id}`, data),
-    onSuccess: (_data, variables) => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.id] });
-    },
-  });
-}
-
-export function useDeleteUnifiedContact() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, hard }: { id: string; hard?: boolean }) =>
-      apiDelete(`/contacts/${id}${hard ? '?hard=true' : ''}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-    },
-  });
-}
-
-export function useContactPersons(contactId?: string) {
-  return useQuery({
-    queryKey: ['unifiedContacts', contactId, 'persons'],
-    queryFn: () => apiGet<{ items: ContactPerson[] }>(`/contacts/${contactId}/persons`),
-    enabled: !!contactId,
-  });
-}
-
-export function useCreateContactPerson() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ contactId, data }: { contactId: string; data: Partial<ContactPerson> }) =>
-      apiPost(`/contacts/${contactId}/persons`, data),
-    onSuccess: (_data, variables) => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId] });
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId, 'persons'] });
-    },
-  });
-}
-
-export function useUpdateContactPerson() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ contactId, personId, data }: { contactId: string; personId: string; data: Partial<ContactPerson> }) =>
-      apiPut(`/contacts/${contactId}/persons/${personId}`, data),
-    onSuccess: (_data, variables) => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId] });
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId, 'persons'] });
-    },
-  });
-}
-
-export function useDeleteContactPerson() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ contactId, personId }: { contactId: string; personId: string }) =>
-      apiDelete(`/contacts/${contactId}/persons/${personId}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-    },
-  });
-}
-
-// Standalone API functions (for non-hook usage)
-export async function fetchContacts(
-  page = 1,
-  pageSize = 25,
-  search?: string,
-  contactType?: string,
-  sortBy?: string,
-  sortOrder?: string,
-): Promise<PaginatedResponse<UnifiedContact>> {
-  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
-  if (search) params.set('search', search);
-  if (contactType) params.set('type', contactType);
-  if (sortBy) params.set('sort_by', sortBy);
-  if (sortOrder) params.set('sort_order', sortOrder);
-  return apiGet<PaginatedResponse<UnifiedContact>>(`/contacts?${params.toString()}`);
-}
-
-export async function fetchContact(id: string): Promise<UnifiedContact & { contact_persons: ContactPerson[] }> {
-  return apiGet<UnifiedContact & { contact_persons: ContactPerson[] }>(`/contacts/${id}`);
-}
-
-export async function createContact(data: Partial<UnifiedContact>): Promise<UnifiedContact> {
-  return apiPost<UnifiedContact>('/contacts', data);
-}
-
-export async function updateContact(id: string, data: Partial<UnifiedContact>): Promise<UnifiedContact> {
-  return apiPut<UnifiedContact>(`/contacts/${id}`, data);
-}
-
-export async function deleteContact(id: string, hard?: boolean): Promise<void> {
-  await apiDelete(`/contacts/${id}${hard ? '?hard=true' : ''}`);
-}
-
-export async function fetchContactPersons(contactId: string): Promise<{ items: ContactPerson[] }> {
-  return apiGet<{ items: ContactPerson[] }>(`/contacts/${contactId}/persons`);
-}
-
-export async function createContactPerson(contactId: string, data: Partial<ContactPerson>): Promise<ContactPerson> {
-  return apiPost<ContactPerson>(`/contacts/${contactId}/persons`, data);
-}
-
-export async function updateContactPerson(contactId: string, personId: string, data: Partial<ContactPerson>): Promise<ContactPerson> {
-  return apiPut<ContactPerson>(`/contacts/${contactId}/persons/${personId}`, data);
-}
-
-export async function deleteContactPerson(contactId: string, personId: string): Promise<void> {
-  await apiDelete(`/contacts/${contactId}/persons/${personId}`);
-}
-
-// ════════════════════════════════════════════════════════════════════════════
-// System Settings, Currency, Tax, Sequence hooks
-// ════════════════════════════════════════════════════════════════════════════
-
-export interface Currency {
-  id: string;
-  code: string;
-  name: string;
-  symbol: string;
-  is_default: boolean;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface TaxRate {
-  id: string;
-  name: string;
-  rate: number;
-  is_default: boolean;
-  country?: string | null;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface Sequence {
-  id: string;
-  name: string;
-  prefix: string;
-  next_number: number;
-  padding: number;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export interface SystemSettings {
-  id?: string;
-  company_name: string;
-  company_legal_form?: string | null;
-  company_street: string;
-  company_city: string;
-  company_zip: string;
-  company_country: string;
-  tax_number?: string | null;
-  vat_id?: string | null;
-  iban?: string | null;
-  bic?: string | null;
-  bank_name?: string | null;
-  ceo?: string | null;
-  trade_register?: string | null;
-  default_currency_id?: string | null;
-  default_tax_id?: string | null;
-  invoice_prefix: string;
-  quote_prefix: string;
-  payment_terms_days: number;
-  created_at?: string;
-  updated_at?: string;
-}
-
-// System Settings
-export function useSystemSettings() {
-  return useQuery({
-    queryKey: ['systemSettings'],
-    queryFn: () => apiGet<SystemSettings>('/system-settings'),
-  });
-}
-
-export function useUpdateSystemSettings() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<SystemSettings>) => apiClient.put('/system-settings', data).then(r => r.data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['systemSettings'] });
-    },
-  });
-}
-
-// Currencies
-export function useCurrencies() {
-  return useQuery({
-    queryKey: ['currencies'],
-    queryFn: () => apiGet<{ items: Currency[]; total: number }>('/currencies'),
-  });
-}
-
-export function useCreateCurrency() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<Currency>) => apiPost('/currencies', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['currencies'] });
-    },
-  });
-}
-
-export function useUpdateCurrency() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<Currency> }) =>
-      apiPatch(`/currencies/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['currencies'] });
-    },
-  });
-}
-
-export function useDeleteCurrency() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/currencies/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['currencies'] });
-    },
-  });
-}
-
-// Taxes
-export function useTaxes() {
-  return useQuery({
-    queryKey: ['taxes'],
-    queryFn: () => apiGet<{ items: TaxRate[]; total: number }>('/taxes'),
-  });
-}
-
-export function useCreateTax() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<TaxRate>) => apiPost('/taxes', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['taxes'] });
-    },
-  });
-}
-
-export function useUpdateTax() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<TaxRate> }) =>
-      apiPatch(`/taxes/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['taxes'] });
-    },
-  });
-}
-
-export function useDeleteTax() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/taxes/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['taxes'] });
-    },
-  });
-}
-
-// Sequences
-export function useSequences() {
-  return useQuery({
-    queryKey: ['sequences'],
-    queryFn: () => apiGet<{ items: Sequence[]; total: number }>('/sequences'),
-  });
-}
-
-export function useCreateSequence() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<Sequence>) => apiPost('/sequences', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['sequences'] });
-    },
-  });
-}
-
-export function useUpdateSequence() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<Sequence> }) =>
-      apiPatch(`/sequences/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['sequences'] });
-    },
-  });
-}
-
-export function useDeleteSequence() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/sequences/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['sequences'] });
-    },
-  });
-}
-
-// Attachments
-export interface Attachment {
-  id: string;
-  entity_type: string;
-  entity_id: string;
-  filename: string;
-  file_path: string;
-  mime_type: string;
-  file_size: number;
-  uploaded_by?: string | null;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export function useAttachments(entityType?: string, entityId?: string) {
-  return useQuery({
-    queryKey: ['attachments', entityType, entityId],
-    queryFn: () => {
-      const params = new URLSearchParams();
-      if (entityType) params.set('entity_type', entityType);
-      if (entityId) params.set('entity_id', entityId);
-      return apiGet<{ items: Attachment[]; total: number }>(`/attachments?${params.toString()}`);
-    },
-    enabled: !!entityType && !!entityId,
-  });
-}
-
-export function useUploadAttachment() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: async ({ file, entityType, entityId }: { file: File; entityType: string; entityId: string }) => {
-      const formData = new FormData();
-      formData.append('file', file);
-      formData.append('entity_type', entityType);
-      formData.append('entity_id', entityId);
-      const response = await apiClient.post('/attachments', formData, {
-        headers: { 'Content-Type': 'multipart/form-data' },
-      });
-      return response.data;
-    },
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['attachments'] });
-    },
-  });
-}
-
-export function useDeleteAttachment() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/attachments/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['attachments'] });
-    },
-  });
-}
-
-// ════════════════════════════════════════════════════════════════════════════
-// Address hooks
-// ════════════════════════════════════════════════════════════════════════════
-
-export interface Address {
-  id: string;
-  entity_type: string;
-  entity_id: string;
-  label: string;
-  address_type: string;
-  street: string | null;
-  street_number: string | null;
-  city: string | null;
-  zip: string | null;
-  state: string | null;
-  country: string | null;
-  is_default: boolean;
-  created_at?: string;
-  updated_at?: string;
-}
-
-export function useAddresses(entityType?: string, entityId?: string) {
-  return useQuery({
-    queryKey: ['addresses', entityType, entityId],
-    queryFn: () =>
-      apiGet<{ items: Address[]; total: number }>(
-        `/addresses?entity_type=${entityType}&entity_id=${entityId}`
-      ),
-    enabled: !!entityType && !!entityId,
-  });
-}
-
-export function useCreateAddress() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<Address> & { entity_type: string; entity_id: string }) =>
-      apiPost('/addresses', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['addresses'] });
-    },
-  });
-}
-
-export function useUpdateAddress() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<Address> }) =>
-      apiPatch(`/addresses/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['addresses'] });
-    },
-  });
-}
-
-export function useDeleteAddress() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/addresses/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['addresses'] });
-    },
-  });
-}
-
-// ════════════════════════════════════════════════════════════════════════════
-// Group hooks
-// ════════════════════════════════════════════════════════════════════════════
-
-export interface Group {
-  id: string;
-  name: string;
-  description: string | null;
-  permissions: Record<string, any>;
-  denied_permissions: string[];
-  field_permissions: Record<string, any>;
-  permission_version: number;
-}
-
-export interface GroupMember {
-  user_id: string;
-  email: string;
-  name: string;
-  is_active: boolean;
-}
-
-export function useGroups() {
-  return useQuery({
-    queryKey: ['groups'],
-    queryFn: () => apiGet<{ items: Group[] }>('/groups'),
-  });
-}
-
-export function useCreateGroup() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: Partial<Group>) => apiPost('/groups', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['groups'] });
-    },
-  });
-}
-
-export function useUpdateGroup() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: Partial<Group> }) =>
-      apiPatch(`/groups/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['groups'] });
-    },
-  });
-}
-
-export function useDeleteGroup() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/groups/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['groups'] });
-    },
-  });
-}
-
-export function useGroupMembers(groupId: string | null) {
-  return useQuery({
-    queryKey: ['groupMembers', groupId],
-    queryFn: () => apiGet<{ items: GroupMember[] }>(`/groups/${groupId}/members`),
-    enabled: !!groupId,
-  });
-}
-
-export function useAddGroupMember() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ groupId, userId }: { groupId: string; userId: string }) =>
-      apiPost(`/groups/${groupId}/members`, { user_id: userId }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['groupMembers'] });
-    },
-  });
-}
-
-export function useRemoveGroupMember() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ groupId, userId }: { groupId: string; userId: string }) =>
-      apiDelete(`/groups/${groupId}/members/${userId}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['groupMembers'] });
-    },
-  });
-}
-
-export function useUserGroups(userId: string | null) {
-  return useQuery({
-    queryKey: ['userGroups', userId],
-    queryFn: () => apiGet<{ items: Group[] }>(`/groups/user/${userId}`),
-    enabled: !!userId,
-  });
-}
-
-// ── Contact Folders ──
-
-export function useContactFolders() {
-  return useQuery({
-    queryKey: ['contactFolders'],
-    queryFn: () => apiGet<import('./contactFolders').ContactFolder[]>('/contact-folders'),
-  });
-}
-
-export function useCreateContactFolder() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (data: { name: string; parent_id?: string }) => apiPost('/contact-folders', data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
-    },
-  });
-}
-
-export function useUpdateContactFolder() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ id, data }: { id: string; data: { name?: string; parent_id?: string | null; sort_order?: number } }) =>
-      apiPut(`/contact-folders/${id}`, data),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
-    },
-  });
-}
-
-export function useDeleteContactFolder() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: (id: string) => apiDelete(`/contact-folders/${id}`),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
-    },
-  });
-}
-
-export function useMoveContactToFolder() {
-  const queryClient = useQueryClient();
-  return useMutation({
-    mutationFn: ({ contactId, folderId }: { contactId: string; folderId: string | null }) =>
-      apiPut(`/contact-folders/contacts/${contactId}/move`, { folder_id: folderId }),
-    onSuccess: () => {
-      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
-      queryClient.invalidateQueries({ queryKey: ['contactFolders'] });
-    },
-  });
-}
-
diff --git a/frontend/src/api/notifications.ts b/frontend/src/api/notifications.ts
new file mode 100644
index 0000000..890b589
--- /dev/null
+++ b/frontend/src/api/notifications.ts
@@ -0,0 +1,77 @@
+/**
+ * Notification hooks: list, unread count, mark read, delete, types, preferences.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPatch, apiDelete } from './client';
+import { PaginatedResponse } from './types';
+
+export interface NotificationTypeItem {
+  type_key: string;
+  plugin_name: string;
+  category: string;
+  label: string;
+  description: string | null;
+  is_enabled_by_default: boolean;
+  is_enabled: boolean;
+}
+
+export function useNotifications() {
+  return useQuery({
+    queryKey: ['notifications'],
+    queryFn: () => apiGet<PaginatedResponse<any>>('/notifications'),
+  });
+}
+
+export function useUnreadNotificationCount() {
+  return useQuery({
+    queryKey: ['notifications', 'unread-count'],
+    queryFn: () => apiGet<number>('/notifications/unread-count'),
+  });
+}
+
+export function useMarkNotificationRead() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiPatch(`/notifications/${id}/read`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['notifications'] });
+    },
+  });
+}
+
+export function useDeleteNotification() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/notifications/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['notifications'] });
+    },
+  });
+}
+
+export function useNotificationTypes() {
+  return useQuery({
+    queryKey: ['notification-types'],
+    queryFn: () => apiGet<{ items: NotificationTypeItem[] }>('/notifications/types'),
+  });
+}
+
+export function useNotificationPreferences() {
+  return useQuery({
+    queryKey: ['notification-preferences'],
+    queryFn: () => apiGet<{ items: { type_key: string; is_enabled: boolean }[] }>('/notifications/preferences'),
+  });
+}
+
+export function useUpdateNotificationPreference() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ typeKey, isEnabled }: { typeKey: string; isEnabled: boolean }) =>
+      apiPatch(`/notifications/preferences/${typeKey}`, { is_enabled: isEnabled }),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['notification-preferences'] });
+      queryClient.invalidateQueries({ queryKey: ['notification-types'] });
+    },
+  });
+}
diff --git a/frontend/src/api/plugins.ts b/frontend/src/api/plugins.ts
new file mode 100644
index 0000000..4b9ea43
--- /dev/null
+++ b/frontend/src/api/plugins.ts
@@ -0,0 +1,67 @@
+/**
+ * Plugin management hooks: list, install, activate, deactivate, uninstall.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiDelete } from './client';
+
+export interface Plugin {
+  name: string;
+  display_name?: string;
+  description?: string;
+  version?: string;
+  status: 'discovered' | 'installed' | 'active' | 'inactive';
+  installed?: boolean;
+  active?: boolean;
+}
+
+export function usePlugins() {
+  return useQuery({
+    queryKey: ['plugins'],
+    queryFn: async () => {
+      const data = await apiGet<any>('/plugins');
+      return data;
+    },
+  });
+}
+
+export function useInstallPlugin() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (name: string) => apiPost(`/plugins/${name}/install`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['plugins'] });
+    },
+  });
+}
+
+export function useActivatePlugin() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (name: string) => apiPost(`/plugins/${name}/activate`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['plugins'] });
+    },
+  });
+}
+
+export function useDeactivatePlugin() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (name: string) => apiPost(`/plugins/${name}/deactivate`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['plugins'] });
+    },
+  });
+}
+
+export function useUninstallPlugin() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ name, removeData }: { name: string; removeData: boolean }) =>
+      apiDelete(`/plugins/${name}?remove_data=${removeData}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['plugins'] });
+    },
+  });
+}
diff --git a/frontend/src/api/roles.ts b/frontend/src/api/roles.ts
new file mode 100644
index 0000000..eaed23d
--- /dev/null
+++ b/frontend/src/api/roles.ts
@@ -0,0 +1,83 @@
+/**
+ * Role and permission hooks.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete } from './client';
+
+export interface Role {
+  id: string;
+  name: string;
+  permissions: Record<string, any>;
+  field_permissions?: Record<string, any>;
+}
+
+export interface PermissionItem {
+  key: string;
+  label: string;
+  category: string;
+  plugin_name?: string;
+}
+
+export interface FieldDefinition {
+  module: string;
+  field: string;
+  label: string;
+  sensitivity: string;
+}
+
+export interface PermissionsResponse {
+  system: PermissionItem[];
+  plugins: PermissionItem[];
+  all: PermissionItem[];
+  field_definitions?: FieldDefinition[];
+}
+
+export function useRoles() {
+  return useQuery({
+    queryKey: ['roles'],
+    queryFn: async () => {
+      const data = await apiGet<any>('/roles');
+      return data;
+    },
+  });
+}
+
+export function usePermissions() {
+  return useQuery({
+    queryKey: ['permissions'],
+    queryFn: () => apiGet<PermissionsResponse>('/roles/permissions'),
+  });
+}
+
+export function useCreateRole() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: { name: string; permissions: Record<string, any>; field_permissions: Record<string, any> }) =>
+      apiPost('/roles', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['roles'] });
+    },
+  });
+}
+
+export function useUpdateRole() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: { name?: string; permissions?: Record<string, any>; field_permissions?: Record<string, any> } }) =>
+      apiPatch(`/roles/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['roles'] });
+    },
+  });
+}
+
+export function useDeleteRole() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/roles/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['roles'] });
+    },
+  });
+}
diff --git a/frontend/src/api/settings.ts b/frontend/src/api/settings.ts
new file mode 100644
index 0000000..2dee837
--- /dev/null
+++ b/frontend/src/api/settings.ts
@@ -0,0 +1,195 @@
+/**
+ * System settings, currency, tax, and sequence hooks.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete, apiClient } from './client';
+
+export interface Currency {
+  id: string;
+  code: string;
+  name: string;
+  symbol: string;
+  is_default: boolean;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface TaxRate {
+  id: string;
+  name: string;
+  rate: number;
+  is_default: boolean;
+  country?: string | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface Sequence {
+  id: string;
+  name: string;
+  prefix: string;
+  next_number: number;
+  padding: number;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface SystemSettings {
+  id?: string;
+  company_name: string;
+  company_legal_form?: string | null;
+  company_street: string;
+  company_city: string;
+  company_zip: string;
+  company_country: string;
+  tax_number?: string | null;
+  vat_id?: string | null;
+  iban?: string | null;
+  bic?: string | null;
+  bank_name?: string | null;
+  ceo?: string | null;
+  trade_register?: string | null;
+  default_currency_id?: string | null;
+  default_tax_id?: string | null;
+  invoice_prefix: string;
+  quote_prefix: string;
+  payment_terms_days: number;
+  created_at?: string;
+  updated_at?: string;
+}
+
+// System Settings
+export function useSystemSettings() {
+  return useQuery({
+    queryKey: ['systemSettings'],
+    queryFn: () => apiGet<SystemSettings>('/system-settings'),
+  });
+}
+
+export function useUpdateSystemSettings() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<SystemSettings>) => apiClient.put('/system-settings', data).then(r => r.data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['systemSettings'] });
+    },
+  });
+}
+
+// Currencies
+export function useCurrencies() {
+  return useQuery({
+    queryKey: ['currencies'],
+    queryFn: () => apiGet<{ items: Currency[]; total: number }>('/currencies'),
+  });
+}
+
+export function useCreateCurrency() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<Currency>) => apiPost('/currencies', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['currencies'] });
+    },
+  });
+}
+
+export function useUpdateCurrency() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<Currency> }) =>
+      apiPatch(`/currencies/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['currencies'] });
+    },
+  });
+}
+
+export function useDeleteCurrency() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/currencies/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['currencies'] });
+    },
+  });
+}
+
+// Taxes
+export function useTaxes() {
+  return useQuery({
+    queryKey: ['taxes'],
+    queryFn: () => apiGet<{ items: TaxRate[]; total: number }>('/taxes'),
+  });
+}
+
+export function useCreateTax() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<TaxRate>) => apiPost('/taxes', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['taxes'] });
+    },
+  });
+}
+
+export function useUpdateTax() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<TaxRate> }) =>
+      apiPatch(`/taxes/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['taxes'] });
+    },
+  });
+}
+
+export function useDeleteTax() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/taxes/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['taxes'] });
+    },
+  });
+}
+
+// Sequences
+export function useSequences() {
+  return useQuery({
+    queryKey: ['sequences'],
+    queryFn: () => apiGet<{ items: Sequence[]; total: number }>('/sequences'),
+  });
+}
+
+export function useCreateSequence() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<Sequence>) => apiPost('/sequences', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['sequences'] });
+    },
+  });
+}
+
+export function useUpdateSequence() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<Sequence> }) =>
+      apiPatch(`/sequences/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['sequences'] });
+    },
+  });
+}
+
+export function useDeleteSequence() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/sequences/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['sequences'] });
+    },
+  });
+}
diff --git a/frontend/src/api/types.ts b/frontend/src/api/types.ts
new file mode 100644
index 0000000..6f54132
--- /dev/null
+++ b/frontend/src/api/types.ts
@@ -0,0 +1,43 @@
+/**
+ * Shared type definitions used across multiple API modules.
+ */
+
+export interface PaginatedResponse<T> {
+  items: T[];
+  total: number;
+  page: number;
+  page_size: number;
+}
+
+export interface Company {
+  id: string;
+  name: string;
+  account_number?: string | null;
+  industry?: string | null;
+  phone?: string | null;
+  email?: string | null;
+  website?: string | null;
+  description?: string | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface CompanyDetail extends Company {
+  contacts?: Contact[];
+}
+
+export interface Contact {
+  id: string;
+  first_name: string;
+  last_name: string;
+  email: string;
+  phone?: string | null;
+  position?: string | null;
+  company_ids?: string[];
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface ContactDetail extends Contact {
+  companies?: Company[];
+}
diff --git a/frontend/src/api/unifiedContacts.ts b/frontend/src/api/unifiedContacts.ts
new file mode 100644
index 0000000..2b9e2aa
--- /dev/null
+++ b/frontend/src/api/unifiedContacts.ts
@@ -0,0 +1,268 @@
+/**
+ * Unified Contact (Rentman-style) hooks and standalone API functions.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPut, apiDelete } from './client';
+import { PaginatedResponse } from './types';
+
+export interface ContactPerson {
+  id: string;
+  contact_id: string;
+  displayname: string;
+  firstname?: string | null;
+  middle_name?: string | null;
+  lastname?: string | null;
+  function?: string | null;
+  phone?: string | null;
+  mobilephone?: string | null;
+  email?: string | null;
+  street?: string | null;
+  number?: string | null;
+  postalcode?: string | null;
+  city?: string | null;
+  state?: string | null;
+  country?: string | null;
+  tags?: string | null;
+  custom?: Record<string, any> | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface UnifiedContact {
+  id: string;
+  type: 'company' | 'person';
+  displayname: string;
+  name?: string | null;
+  firstname?: string | null;
+  surname?: string | null;
+  surfix?: string | null;
+  ext_name_line?: string | null;
+  gender?: string | null;
+  code?: string | null;
+  accounting_code?: string | null;
+  vendor_accounting_code?: string | null;
+  // Mailing address
+  mailing_street?: string | null;
+  mailing_number?: string | null;
+  mailing_unit_number?: string | null;
+  mailing_district?: string | null;
+  mailing_extra_address_line?: string | null;
+  mailing_postalcode?: string | null;
+  mailing_city?: string | null;
+  mailing_state?: string | null;
+  mailing_country?: string | null;
+  // Visit address
+  visit_street?: string | null;
+  visit_number?: string | null;
+  visit_unit_number?: string | null;
+  visit_district?: string | null;
+  visit_extra_address_line?: string | null;
+  visit_postalcode?: string | null;
+  visit_city?: string | null;
+  visit_state?: string | null;
+  // Invoice address
+  invoice_street?: string | null;
+  invoice_number?: string | null;
+  invoice_unit_number?: string | null;
+  invoice_district?: string | null;
+  invoice_extra_address_line?: string | null;
+  invoice_postalcode?: string | null;
+  invoice_city?: string | null;
+  invoice_state?: string | null;
+  invoice_country?: string | null;
+  country?: string | null;
+  // Communication
+  phone_1?: string | null;
+  phone_2?: string | null;
+  email_1?: string | null;
+  email_2?: string | null;
+  website?: string | null;
+  // Financial
+  vat_code?: string | null;
+  fiscal_code?: string | null;
+  commerce_code?: string | null;
+  purchase_number?: string | null;
+  bic?: string | null;
+  bank_account?: string | null;
+  // Discounts
+  discount_crew: number;
+  discount_transport: number;
+  discount_rental: number;
+  discount_sale: number;
+  discount_subrent: number;
+  discount_total: number;
+  // Geo
+  latitude?: number | null;
+  longitude?: number | null;
+  // Notes
+  projectnote?: string | null;
+  projectnote_title?: string | null;
+  contact_warning?: string | null;
+  tags?: string | null;
+  image?: string | null;
+  custom?: Record<string, any> | null;
+  folder_id?: string | null;
+  default_person_id?: string | null;
+  admin_contactperson_id?: string | null;
+  contact_persons?: ContactPerson[];
+  created_at?: string;
+  updated_at?: string;
+}
+
+export function useUnifiedContacts(
+  page = 1,
+  pageSize = 25,
+  search?: string,
+  contactType?: string,
+  sortBy?: string,
+  sortOrder?: string,
+  folderId?: string,
+) {
+  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
+  if (search) params.set('search', search);
+  if (contactType) params.set('type', contactType);
+  if (sortBy) params.set('sort_by', sortBy);
+  if (sortOrder) params.set('sort_order', sortOrder);
+  if (folderId) params.set('folder_id', folderId);
+  return useQuery({
+    queryKey: ['unifiedContacts', page, pageSize, search, contactType, sortBy, sortOrder, folderId],
+    queryFn: () =>
+      apiGet<PaginatedResponse<UnifiedContact>>(`/contacts?${params.toString()}`),
+  });
+}
+
+export function useUnifiedContact(id?: string) {
+  return useQuery({
+    queryKey: ['unifiedContacts', id],
+    queryFn: () => apiGet<UnifiedContact & { contact_persons: ContactPerson[] }>(`/contacts/${id}`),
+    enabled: !!id,
+  });
+}
+
+export function useCreateUnifiedContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: Partial<UnifiedContact>) => apiPost('/contacts', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+    },
+  });
+}
+
+export function useUpdateUnifiedContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: Partial<UnifiedContact> }) =>
+      apiPut(`/contacts/${id}`, data),
+    onSuccess: (_data, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.id] });
+    },
+  });
+}
+
+export function useDeleteUnifiedContact() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, hard }: { id: string; hard?: boolean }) =>
+      apiDelete(`/contacts/${id}${hard ? '?hard=true' : ''}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+    },
+  });
+}
+
+export function useContactPersons(contactId?: string) {
+  return useQuery({
+    queryKey: ['unifiedContacts', contactId, 'persons'],
+    queryFn: () => apiGet<{ items: ContactPerson[] }>(`/contacts/${contactId}/persons`),
+    enabled: !!contactId,
+  });
+}
+
+export function useCreateContactPerson() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ contactId, data }: { contactId: string; data: Partial<ContactPerson> }) =>
+      apiPost(`/contacts/${contactId}/persons`, data),
+    onSuccess: (_data, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId] });
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId, 'persons'] });
+    },
+  });
+}
+
+export function useUpdateContactPerson() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ contactId, personId, data }: { contactId: string; personId: string; data: Partial<ContactPerson> }) =>
+      apiPut(`/contacts/${contactId}/persons/${personId}`, data),
+    onSuccess: (_data, variables) => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId] });
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts', variables.contactId, 'persons'] });
+    },
+  });
+}
+
+export function useDeleteContactPerson() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ contactId, personId }: { contactId: string; personId: string }) =>
+      apiDelete(`/contacts/${contactId}/persons/${personId}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['unifiedContacts'] });
+    },
+  });
+}
+
+// Standalone API functions (for non-hook usage)
+export async function fetchContacts(
+  page = 1,
+  pageSize = 25,
+  search?: string,
+  contactType?: string,
+  sortBy?: string,
+  sortOrder?: string,
+): Promise<PaginatedResponse<UnifiedContact>> {
+  const params = new URLSearchParams({ page: String(page), page_size: String(pageSize) });
+  if (search) params.set('search', search);
+  if (contactType) params.set('type', contactType);
+  if (sortBy) params.set('sort_by', sortBy);
+  if (sortOrder) params.set('sort_order', sortOrder);
+  return apiGet<PaginatedResponse<UnifiedContact>>(`/contacts?${params.toString()}`);
+}
+
+export async function fetchContact(id: string): Promise<UnifiedContact & { contact_persons: ContactPerson[] }> {
+  return apiGet<UnifiedContact & { contact_persons: ContactPerson[] }>(`/contacts/${id}`);
+}
+
+export async function createContact(data: Partial<UnifiedContact>): Promise<UnifiedContact> {
+  return apiPost<UnifiedContact>('/contacts', data);
+}
+
+export async function updateContact(id: string, data: Partial<UnifiedContact>): Promise<UnifiedContact> {
+  return apiPut<UnifiedContact>(`/contacts/${id}`, data);
+}
+
+export async function deleteContact(id: string, hard?: boolean): Promise<void> {
+  await apiDelete(`/contacts/${id}${hard ? '?hard=true' : ''}`);
+}
+
+export async function fetchContactPersons(contactId: string): Promise<{ items: ContactPerson[] }> {
+  return apiGet<{ items: ContactPerson[] }>(`/contacts/${contactId}/persons`);
+}
+
+export async function createContactPerson(contactId: string, data: Partial<ContactPerson>): Promise<ContactPerson> {
+  return apiPost<ContactPerson>(`/contacts/${contactId}/persons`, data);
+}
+
+export async function updateContactPerson(contactId: string, personId: string, data: Partial<ContactPerson>): Promise<ContactPerson> {
+  return apiPut<ContactPerson>(`/contacts/${contactId}/persons/${personId}`, data);
+}
+
+export async function deleteContactPerson(contactId: string, personId: string): Promise<void> {
+  await apiDelete(`/contacts/${contactId}/persons/${personId}`);
+}
diff --git a/frontend/src/api/users.ts b/frontend/src/api/users.ts
new file mode 100644
index 0000000..d29ad45
--- /dev/null
+++ b/frontend/src/api/users.ts
@@ -0,0 +1,54 @@
+/**
+ * User CRUD hooks.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiPatch, apiDelete } from './client';
+import { PaginatedResponse } from './types';
+
+export function useUsers(page = 1, pageSize = 25) {
+  return useQuery({
+    queryKey: ['users', page, pageSize],
+    queryFn: () =>
+      apiGet<PaginatedResponse<any>>(`/users?page=${page}&page_size=${pageSize}`),
+  });
+}
+
+export function useUser(id?: string) {
+  return useQuery({
+    queryKey: ['users', id],
+    queryFn: () => apiGet<any>(`/users/${id}`),
+    enabled: !!id,
+  });
+}
+
+export function useCreateUser() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: any) => apiPost('/users', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['users'] });
+    },
+  });
+}
+
+export function useUpdateUser() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, data }: { id: string; data: any }) =>
+      apiPatch(`/users/${id}`, data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['users'] });
+    },
+  });
+}
+
+export function useDeleteUser() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/users/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['users'] });
+    },
+  });
+}