feat: unified_search + ai_proactive plugins with Ollama Cloud DeepSeek V4

- unified_search: Hybride Suche (PostgreSQL FTS + pgvector + RRF Fusion)
  - 5 Search Providers (Contact, Company, Mail, File, Event)
  - KI Query Understanding (Fuzzy, Facetten via LiteLLM)
  - DMS Text-Extraction (PDF, DOCX, XLSX, PPTX)
  - Embedding Pipeline (ollama/nomic-embed-text, 768 Dim)
  - Background Jobs für Indexierung
  - Plugin-basierte Provider Registry

- ai_proactive: Proaktiver KI-Agent
  - Context-Tracking (Frontend → Backend → Event Bus)
  - Proactive Engine mit LLM Suggestion-Generierung
  - SSE Real-time Push an Frontend
  - 6 AI Tools für Tool Registry
  - Rate-Limiting + User Settings
  - Deep Analysis Background Jobs

- Frontend Integration:
  - useAIContext Hook, SuggestionSidebar, SuggestionBadge
  - ProactiveAISettings Page, Search API Client
  - Globale Suche auf neue API umgestellt

- Tests: test_unified_search.py + test_ai_proactive.py (alle bestanden)
- Config: Ollama Cloud DeepSeek V4 als Default, konfigurierbar
- Dependencies: PyMuPDF, python-docx, python-pptx, pgvector
- Bugfixes: notification type_key length, migration IF NOT EXISTS

frontend/src/hooks/useAIContext.ts

@@ -0,0 +1,24 @@
+import { useEffect, useRef } from 'react';
+import { useLocation } from 'react-router-dom';
+import { apiClient } from '@/api/client';
+
+export function useAIContext(entityType?: string, entityId?: string, entityData?: any) {
+  const location = useLocation();
+  const debounceRef = useRef<ReturnType<typeof setTimeout>>();
+
+  useEffect(() => {
+    if (debounceRef.current) clearTimeout(debounceRef.current);
+    debounceRef.current = setTimeout(() => {
+      apiClient.post('/api/v1/ai-proactive/context', {
+        page: location.pathname,
+        entity_type: entityType,
+        entity_id: entityId,
+        entity_data: entityData,
+      }).catch(() => {}); // Silent fail, don't bother user
+    }, 500); // Debounce 500ms
+
+    return () => {
+      if (debounceRef.current) clearTimeout(debounceRef.current);
+    };
+  }, [location.pathname, entityType, entityId, entityData]);
+}