feat: notification batching, per-folder mute, and global pause

Debounce embedding/tagging completion notifications per folder (6s window)
so rapid file additions from downloaders fire one notification instead of
one per file. Add per-folder mute via the sidebar context menu and a global
pause toggle in Settings > General, both persisted across restarts.

src/App.tsx

@@ -18,11 +18,15 @@ export default function App() {
   const loadImages = useGalleryStore((state) => state.loadImages);
   const loadCaptionModelStatus = useGalleryStore((state) => state.loadCaptionModelStatus);
   const loadDuplicateScanCache = useGalleryStore((state) => state.loadDuplicateScanCache);
+  const loadMutedFolderIds = useGalleryStore((state) => state.loadMutedFolderIds);
+  const loadNotificationsPaused = useGalleryStore((state) => state.loadNotificationsPaused);
   const subscribeToProgress = useGalleryStore((state) => state.subscribeToProgress);
   const activeView = useGalleryStore((state) => state.activeView);
 
   useEffect(() => {
     void initializeNotifications();
+    void loadMutedFolderIds();
+    void loadNotificationsPaused();
     loadFolders().then(() => {
       void loadBackgroundJobProgress();
       void loadCaptionModelStatus();