fix: chat — show group avatar in room list

src/components/chat/ChatWidget.tsx

@@ -1105,9 +1105,11 @@ function RoomRow({ room, isPinned, isMuted, isOnline, onClick, onMenuClick }: {
             <Bell size={16} className="text-amber-600 dark:text-amber-400" />
           </div>
         ) : room.type === 'group' ? (
-          <div className="w-9 h-9 rounded-full bg-violet-100 dark:bg-violet-900/30 flex items-center justify-center">
-            <Users size={16} className="text-violet-600 dark:text-violet-400" />
-          </div>
+          room.avatarUrl
+            ? <img src={room.avatarUrl} alt={room.name ?? ''} className="w-9 h-9 rounded-full object-cover" />
+            : <div className="w-9 h-9 rounded-full bg-violet-100 dark:bg-violet-900/30 flex items-center justify-center">
+                <Users size={16} className="text-violet-600 dark:text-violet-400" />
+              </div>
         ) : (
           <Avatar name={room.otherUserName ?? '?'} size={36} online={isOnline} />
         )}