Mark async socket handling task done and implement startup cleanup

backend/app/startup.py

@@ -7,6 +7,7 @@ in ``app.main`` delegates resource creation and task registration here.
 
 from __future__ import annotations
 
+from contextlib import suppress
 from pathlib import Path
 
 import aiohttp
@@ -101,13 +102,22 @@ async def startup_shared_resources(
     http_session: aiohttp.ClientSession = _create_http_session(settings)
     geo_service.init_geoip(settings.geoip_db_path)
 
-    scheduler: AsyncIOScheduler = AsyncIOScheduler(timezone="UTC")
-    scheduler.start()
+    scheduler: AsyncIOScheduler | None = None
+    try:
+        scheduler = AsyncIOScheduler(timezone="UTC")
+        scheduler.start()
 
-    health_check.register(app)
-    blocklist_import.register(app)
-    geo_cache_flush.register(app)
-    geo_re_resolve.register(app)
-    history_sync.register(app)
+        health_check.register(app)
+        blocklist_import.register(app)
+        geo_cache_flush.register(app)
+        geo_re_resolve.register(app)
+        history_sync.register(app)
 
-    return http_session, scheduler
+        return http_session, scheduler
+    except Exception:
+        with suppress(Exception):
+            await http_session.close()
+        if scheduler is not None:
+            with suppress(Exception):
+                scheduler.shutdown(wait=False)
+        raise