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

app/plugins/builtins/unified_search/models.py

@@ -0,0 +1,50 @@
+"""SQLAlchemy models for the Unified Search plugin."""
+
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, Index, String, Text
+from sqlalchemy.dialects.postgresql import JSONB, UUID as PGUUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.db import Base, TenantMixin
+
+
+class SearchProviderRegistry(Base, TenantMixin):
+    """Registry of active search providers per tenant."""
+
+    __tablename__ = "unified_search_providers"
+    __table_args__ = (
+        Index("ix_usp_tenant", "tenant_id"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    entity_type: Mapped[str] = mapped_column(String(50), nullable=False)
+    plugin_name: Mapped[str] = mapped_column(String(80), nullable=False)
+    is_active: Mapped[bool] = mapped_column(
+        nullable=False, default=True
+    )
+    config: Mapped[dict] = mapped_column(JSONB, nullable=False, default=dict)
+
+
+class SearchIndexLog(Base, TenantMixin):
+    """Log of indexing actions for audit and debugging."""
+
+    __tablename__ = "unified_search_index_log"
+    __table_args__ = (
+        Index("ix_usil_tenant", "tenant_id"),
+        Index("ix_usil_entity", "entity_type", "entity_id"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    entity_type: Mapped[str] = mapped_column(String(50), nullable=False)
+    entity_id: Mapped[uuid.UUID] = mapped_column(PGUUID(as_uuid=True), nullable=False)
+    action: Mapped[str] = mapped_column(String(20), nullable=False)
+    status: Mapped[str] = mapped_column(String(20), nullable=False, default="pending")
+    error_message: Mapped[str | None] = mapped_column(Text, nullable=True)