fixed stalled requests after app resume

lib/state/app/modules/chat/bloc/chat_bloc.dart

@@ -23,6 +23,9 @@ class ChatBloc
   final ChatListBloc? _chatListBloc;
 
   String? _pollingToken;
+  // A loop parked in its request survives stop+start for the same token
+  // (pause/resume); the generation retires it so only one loop polls.
+  int _pollGeneration = 0;
   int _backoffMs = 0;
   int _lastKnownMessageId = 0;
   bool _appResumed = true;
@@ -265,23 +268,25 @@ class ChatBloc
     _pollingToken = token;
     _backoffMs = 0;
     _lastKnownMessageId = _maxMessageId(innerState?.chatResponse);
-    unawaited(_pollLoop(token));
+    unawaited(_pollLoop(token, ++_pollGeneration));
   }
 
   void _stopLongPoll() {
     _pollingToken = null;
+    _pollGeneration++;
     _backoffMs = 0;
   }
 
-  Future<void> _pollLoop(String token) async {
-    while (_pollingToken == token && !isClosed) {
+  Future<void> _pollLoop(String token, int generation) async {
+    bool active() => generation == _pollGeneration && !isClosed;
+    while (active()) {
       try {
         final response = await LongPollChat(
           chatToken: token,
           lastKnownMessageId: _lastKnownMessageId,
         ).run();
 
-        if (_pollingToken != token || isClosed) return;
+        if (!active()) return;
         _backoffMs = 0;
 
         if (response == null) continue;
@@ -305,7 +310,7 @@ class ChatBloc
           _chatListBloc?.markRoomAsRead(token, _lastKnownMessageId);
         }
       } on Object catch (e) {
-        if (_pollingToken != token || isClosed) return;
+        if (!active()) return;
         log('LongPoll error for $token: $e');
         _backoffMs = _backoffMs == 0 ? 2000 : math.min(_backoffMs * 2, 30000);
         await Future.delayed(Duration(milliseconds: _backoffMs));