feat(5.22): Saved Searches / Smart Lists — reusable filters for list views

- SavedFilter model with TenantMixin (name, entity_type, filter_criteria JSONB, user_id)
- Routes: GET/POST /saved-filters, DELETE /saved-filters/{id} with RBAC
- Alembic migration 0029_saved_filters creates saved_filters table
- Frontend: SavedFilters.tsx component with save/load/delete UI
- Frontend: api/savedFilters.ts with React Query hooks
- Integrated into ContactsListPage as example
- i18n keys for savedFilters.* in de.json and en.json
- Tests: test_saved_filters.py (9 tests) + SavedFilters.test.tsx (3 tests)
- Registered SavedFilter in conftest.py

frontend/src/api/savedFilters.ts

@@ -0,0 +1,51 @@
+/**
+ * Saved filters API hooks — CRUD for reusable filter criteria.
+ */
+
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiGet, apiPost, apiDelete } from './client';
+
+export interface SavedFilter {
+  id: string;
+  name: string;
+  entity_type: string;
+  filter_criteria: Record<string, any>;
+  user_id: string;
+  created_at: string;
+  updated_at: string;
+}
+
+export interface SavedFilterCreateInput {
+  name: string;
+  entity_type: string;
+  filter_criteria: Record<string, any>;
+}
+
+export function useSavedFilters(entityType?: string) {
+  const params = new URLSearchParams();
+  if (entityType) params.set('entity_type', entityType);
+  return useQuery({
+    queryKey: ['saved-filters', entityType],
+    queryFn: () => apiGet<SavedFilter[]>(`/saved-filters?${params.toString()}`),
+  });
+}
+
+export function useCreateSavedFilter() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (data: SavedFilterCreateInput) => apiPost<SavedFilter>('/saved-filters', data),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['saved-filters'] });
+    },
+  });
+}
+
+export function useDeleteSavedFilter() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => apiDelete(`/saved-filters/${id}`),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['saved-filters'] });
+    },
+  });
+}