fix(monitoring): repair silent-false-positive update badge + auto-update scheduling

Customer container status checks looked up containers by an exact expected
name. When a docker compose recreate got interrupted (e.g. a hung command
previously killed the whole update-all batch on timeout), Compose could leave
the old container renamed with a random hash prefix instead of removed. The
exact-name lookup then found nothing, returned None, and that silently
counted as "up to date" (green "Aktuell") instead of surfacing as unknown —
affecting 5 customers on the appliance whose containers were actually still
running under orphaned names.

- _run_cmd no longer raises on subprocess timeout, so one stuck customer
  can't abort the rest of a batch update
- repair_container_naming() self-heals orphaned hash-renamed containers by
  renaming them back before every status check and before recreate
- update-all loop now catches per-customer exceptions instead of aborting
- status responses expose "unknown" separately from "needs_update" so the UI
  shows a distinct grey badge instead of a false-positive green one
- new settings: automatic daily update check (on/off + time), with an
  independent toggle for whether it also auto-recreates customer containers

app/main.py

@@ -13,6 +13,7 @@ from slowapi.errors import RateLimitExceeded
 from app.database import init_db
 from app.limiter import limiter
 from app.routers import auth, customers, deployments, monitoring, settings, users
+from app.services import scheduler_service
 
 # ---------------------------------------------------------------------------
 # Logging
@@ -140,3 +141,10 @@ async def startup_event():
     logger.info("Starting NetBird MSP Appliance...")
     init_db()
     logger.info("Database initialized.")
+    scheduler_service.start()
+
+
+@app.on_event("shutdown")
+async def shutdown_event():
+    """Stop background tasks on shutdown."""
+    scheduler_service.stop()