implemented chat long-polling and optimistic updates, centralized notification management, optimized avatar caching

lib/app.dart

@@ -36,7 +36,6 @@ class App extends StatefulWidget {
 }
 
 class _AppState extends State<App> with WidgetsBindingObserver {
-  late Timer _refetchChats;
   late Timer _updateTimings;
   StreamSubscription<dynamic>? _timetableWidgetSync;
   // Tracked via the bottom-nav controller's listener so it always reflects the
@@ -45,8 +44,25 @@ class _AppState extends State<App> with WidgetsBindingObserver {
   int _knownTotalTabs = 1;
   bool _userOnLastTab = false;
 
+  static const Duration _chatListActiveInterval = Duration(seconds: 15);
+  static const Duration _chatListIdleInterval = Duration(seconds: 60);
+
   void _onTabControllerChanged() {
     _userOnLastTab = Main.bottomNavigator.index == _knownTotalTabs - 1;
+    _syncChatListPolling();
+  }
+
+  void _syncChatListPolling() {
+    if (!mounted) return;
+    final modules = AppModule.getBottomBarModules(context);
+    final talkSlot = modules.indexWhere((m) => m.module == Modules.talk);
+    final talkIsActive =
+        talkSlot >= 0 && Main.bottomNavigator.index == talkSlot;
+    final bloc = context.read<ChatListBloc>();
+    bloc.setAutoRefreshInterval(
+      talkIsActive ? _chatListActiveInterval : _chatListIdleInterval,
+    );
+    if (talkIsActive) bloc.refresh();
   }
 
   @override
@@ -138,19 +154,13 @@ class _AppState extends State<App> with WidgetsBindingObserver {
       ShareIntentListener.instance.attach();
       ShareIntentListener.pending.addListener(_handlePendingShare);
       _handlePendingShare();
+      _syncChatListPolling();
     });
 
     _updateTimings = Timer.periodic(const Duration(seconds: 30), (_) {
       if (mounted) setState(() {});
     });
 
-    _refetchChats = Timer.periodic(const Duration(seconds: 60), (_) {
-      WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (!mounted) return;
-        context.read<ChatListBloc>().refresh();
-      });
-    });
-
     UpdateUserIndex.index();
 
     if (context.read<SettingsCubit>().val().notificationSettings.enabled) {
@@ -181,7 +191,6 @@ class _AppState extends State<App> with WidgetsBindingObserver {
 
   @override
   void dispose() {
-    _refetchChats.cancel();
     _updateTimings.cancel();
     _timetableWidgetSync?.cancel();
     ShareIntentListener.pending.removeListener(_handlePendingShare);