optimized avatar and linkify performance, refined navigation to preserve popups, implemented read marker caching, and added file size limits for saving, minor timetable details changes

lib/state/app/modules/chat_list/bloc/chat_list_bloc.dart

@@ -107,6 +107,19 @@ class ChatListBloc
     await refresh();
   }
 
+  /// Returns the cached `lastReadMessage` for the room with [token], or
+  /// `null` if the room is not (yet) known. Used by [ChatBloc] to skip
+  /// redundant server read-marker calls when the local cache already
+  /// reflects the same position.
+  int? lastReadMessageFor(String token) {
+    final rooms = innerState?.rooms;
+    if (rooms == null) return null;
+    for (final room in rooms.data) {
+      if (room.token == token) return room.lastReadMessage;
+    }
+    return null;
+  }
+
   /// Optimistically clears the unread counter for [token] so the tile
   /// reacts before a refresh roundtrip lands. Server-side mark-as-read
   /// is the caller's job (see [ChatBloc.sendServerReadMarker]).