feat: Intelligente Telegram-Kanal-Selektion und verbesserte Quellenzuordnung

- Researcher: Claude-basierte Vorauswahl relevanter Telegram-Kanäle per Haiku
- FactChecker: Verbesserte Quellen-Zuordnung mit Relevanz-Scoring (Top 5)
- FactChecker: URLs werden nicht mehr doppelt zugeordnet, sources_count wird aktualisiert
- TelegramParser: Kanal-Filterung per channel_ids statt categories
- TelegramParser: Lockereres Keyword-Matching (1 Match reicht, da vorselektiert)
- Models: telegram_categories Feld entfernt (durch KI-Selektion ersetzt)
- Main: Chat-Router eingebunden unter /api/chat

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main.py

@@ -331,6 +331,7 @@ from routers.sources import router as sources_router
 from routers.notifications import router as notifications_router
 from routers.feedback import router as feedback_router
 from routers.public_api import router as public_api_router
+from routers.chat import router as chat_router
 
 app.include_router(auth_router)
 app.include_router(incidents_router)
@@ -338,6 +339,7 @@ app.include_router(sources_router)
 app.include_router(notifications_router)
 app.include_router(feedback_router)
 app.include_router(public_api_router)
+app.include_router(chat_router, prefix="/api/chat")
 
 
 @app.websocket("/api/ws")