fix(web): notification media preview and theme switching

- show media labels instead of raw URLs in browser notifications

- support notification icon preview for image messages

- implement effective light/dark/system theme application

- apply appearance prefs on app startup

web/src/app/App.tsx

@@ -5,6 +5,7 @@ import { AuthPage } from "../pages/AuthPage";
 import { ChatsPage } from "../pages/ChatsPage";
 import { useAuthStore } from "../store/authStore";
 import { useChatStore } from "../store/chatStore";
+import { applyAppearancePreferences, getAppPreferences } from "../utils/preferences";
 
 const PENDING_INVITE_TOKEN_KEY = "bm_pending_invite_token";
 
@@ -18,6 +19,10 @@ export function App() {
   const setActiveChatId = useChatStore((s) => s.setActiveChatId);
   const [joiningInvite, setJoiningInvite] = useState(false);
 
+  useEffect(() => {
+    applyAppearancePreferences(getAppPreferences());
+  }, []);
+
   useEffect(() => {
     if (!accessToken) {
       return;