feat: asset-based image/video sources, notification sounds, UI improvements

- Replace URL-based image_source/url fields with image_asset_id/video_asset_id
  on StaticImagePictureSource and VideoCaptureSource (clean break, no migration)
- Resolve asset IDs to file paths at runtime via AssetStore.get_file_path()
- Add EntitySelect asset pickers for image/video in stream editor modal
- Add notification sound configuration (global sound + per-app overrides)
- Unify per-app color and sound overrides into single "Per-App Overrides" section
- Persist notification history between server restarts
- Add asset management system (upload, edit, delete, soft-delete)
- Replace emoji buttons with SVG icons throughout UI
- Various backend improvements: SQLite stores, auth, backup, MQTT, webhooks

server/src/wled_controller/server_ref.py

@@ -7,6 +7,10 @@ mechanism the system tray "Shutdown" menu item uses.
 
 from typing import Any, Optional
 
+from wled_controller.utils import get_logger
+
+logger = get_logger(__name__)
+
 _server: Optional[Any] = None  # uvicorn.Server
 _tray: Optional[Any] = None    # TrayManager
 
@@ -39,7 +43,8 @@ def request_shutdown() -> None:
     try:
         from wled_controller.main import _save_all_stores
         _save_all_stores()
-    except Exception:
+    except Exception as e:
+        logger.debug("Best-effort store save on shutdown failed: %s", e)
         pass  # best-effort; lifespan handler is the backup
 
     if _server is not None:
@@ -55,5 +60,6 @@ def _broadcast_restarting() -> None:
         pm = _deps.get("processor_manager")
         if pm is not None:
             pm.fire_event({"type": "server_restarting"})
-    except Exception:
+    except Exception as e:
+        logger.debug("Failed to broadcast server_restarting event: %s", e)
         pass