Update-System: /api/version + /api/release-notes + RELEASES.json

Frontend kann jetzt erkennen, wann eine neue Version live ist, und dem Nutzer
einen passenden Hinweis sowie die Release-Notes anzeigen.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.py

@@ -378,6 +378,7 @@ 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
 from routers.tutorial import router as tutorial_router
+from routes.version_router import router as version_router
 
 app.include_router(auth_router)
 app.include_router(incidents_router)
@@ -387,6 +388,7 @@ app.include_router(feedback_router)
 app.include_router(public_api_router)
 app.include_router(chat_router, prefix="/api/chat")
 app.include_router(tutorial_router)
+app.include_router(version_router)
 
 
 @app.websocket("/api/ws")