feat: Tutorial-Fortschritt serverseitig persistieren (Resume/Restart)

- Neuer Router /api/tutorial mit GET/PUT/DELETE für Fortschritt pro User
- DB-Migration: tutorial_step + tutorial_completed in users-Tabelle
- Resume-Dialog bei abgebrochenem Tutorial (Fortsetzen/Neu starten)
- Chat-Hinweis passt sich dem Tutorial-Status dynamisch an
- API-Methoden: getTutorialState, saveTutorialState, resetTutorialState

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

src/main.py

@@ -333,6 +333,7 @@ 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.network_analysis import router as network_analysis_router
+from routers.tutorial import router as tutorial_router
 
 app.include_router(auth_router)
 app.include_router(incidents_router)
@@ -342,6 +343,7 @@ app.include_router(feedback_router)
 app.include_router(public_api_router)
 app.include_router(chat_router, prefix="/api/chat")
 app.include_router(network_analysis_router)
+app.include_router(tutorial_router)
 
 
 @app.websocket("/api/ws")