Phase 0 Complete: Tasks 0.7-0.20

- 0.7: UI-Design-Richtlinien (docs/ui-design-guidelines.md, 535 lines)
- 0.8: Theme-Customization Backend (4 theme fields, migration 0023)
- 0.9: Theme-Customization Frontend (SettingsTheme.tsx, themeStore.ts, live preview)
- 0.10: RBAC-Audit (4 plugins secured, 53 routes with require_permission)
- 0.11: LiteLLM-Cleanup (llm_client.py migrated from httpx to litellm)
- 0.12: KI-Agent-Framework docs (plugin-development-guide.md, agent_capabilities field)
- 0.13: Heartbeat configurable (ProactiveSettings, migration 0024, frontend UI)
- 0.14: Unified Search Field-Level RBAC (resolve_permissions + filter_fields_by_permission)
- 0.15: Undo/History-System (EntityHistory model, service, routes, migration 0025, HistoryViewer)
- 0.16: Storage Backend (LocalStorage + S3Storage, DMS/attachments/mail updated)
- 0.17: Import/Export unified Contact fields (firstname, surname, email_1, phone_1)
- 0.18: .gitignore & Config-Cleanup (webui→frontend, python-jose removed, .env untracked)
- 0.19: Mail-Salt Security-Fix (per-account random salt, migration 0026)
- 0.20: AGPL replaced (PyMuPDF→pypdf, OnlyOffice→Collabora, LICENSE + THIRD_PARTY_LICENSES.md)

frontend/src/api/entityHistory.ts

@@ -0,0 +1,58 @@
+/**
+ * Entity History hooks — undo/restore functionality.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiClient } from './client';
+
+export interface EntityHistoryEntry {
+  id: string;
+  entity_type: string;
+  entity_id: string;
+  action: 'create' | 'update' | 'delete';
+  snapshot_before: Record<string, any> | null;
+  snapshot_after: Record<string, any> | null;
+  changes: Record<string, { old: any; new: any }> | null;
+  user_id: string | null;
+  created_at: string;
+}
+
+export interface EntityHistoryList {
+  items: EntityHistoryEntry[];
+  total: number;
+}
+
+export function useEntityHistory(entityType?: string, entityId?: string) {
+  return useQuery({
+    queryKey: ['entityHistory', entityType, entityId],
+    queryFn: () =>
+      apiGet<EntityHistoryList>(`/entity-history/${entityType}/${entityId}`),
+    enabled: !!entityType && !!entityId,
+  });
+}
+
+export function useRestoreFromHistory() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (historyId: string) =>
+      apiClient.post('/entity-history/restore', { history_id: historyId }).then(r => r.data),
+    onSuccess: (_data, _variables, context) => {
+      queryClient.invalidateQueries({ queryKey: ['entityHistory'] });
+      queryClient.invalidateQueries({ queryKey: ['contacts'] });
+      queryClient.invalidateQueries({ queryKey: ['contact'] });
+    },
+  });
+}
+
+export function useUndoLastAction() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: ({ entityType, entityId }: { entityType: string; entityId: string }) =>
+      apiPost(`/entity-history/undo/${entityType}/${entityId}`, {}),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['entityHistory'] });
+      queryClient.invalidateQueries({ queryKey: ['contacts'] });
+      queryClient.invalidateQueries({ queryKey: ['contact'] });
+    },
+  });
+}

frontend/src/api/settings.ts

@@ -55,6 +55,11 @@ export interface SystemSettings {
   invoice_prefix: string;
   quote_prefix: string;
   payment_terms_days: number;
+  // Theme customization
+  theme_primary_color?: string;
+  theme_accent_color?: string;
+  theme_font_family?: string;
+  theme_border_radius?: string;
   created_at?: string;
   updated_at?: string;
 }