feat: Implement push notification suppression for active chats, prevent duplicate self-messages, update the chat typing indicator, and add back buttons to static screens.

lib/features/messaging/presentation/providers/messaging_provider.dart

@@ -100,6 +100,10 @@ class MessagingNotifier extends StateNotifier<MessagingState> {
       // Avoid duplicates (broadcast may arrive after ack for sender's own message)
       if (currentMessages.any((m) => m.id == message.id)) return;
 
+      // Ignore own messages — the sender path handles these via sendMessage()
+      final isMine = message.senderId == _currentUserId;
+      if (isMine) return;
+
       currentMessages.insert(0, message);
       final updatedMessages =
           Map<String, List<ChatMessage>>.from(state.messages)