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/core/services/push_notification_service.dart

@@ -29,6 +29,10 @@ class PushNotificationService {
   /// Callback when user taps a notification — set by the app to navigate.
   void Function(String? actionUrl)? onNotificationTap;
 
+  /// The conversation ID currently being viewed — suppress message push
+  /// notifications for this conversation to avoid self-notifications.
+  String? activeConversationId;
+
   /// Initialize Firebase Messaging and local notifications.
   Future<void> initialize() async {
     if (_initialized) return;
@@ -159,6 +163,14 @@ class PushNotificationService {
     final notification = message.notification;
     if (notification == null) return;
 
+    // Suppress message push notifications when user is viewing that conversation
+    final msgType = message.data['type'] as String?;
+    final convId = message.data['conversationId'] as String?;
+    if (msgType == 'message' && convId != null && convId == activeConversationId) {
+      debugPrint('[FCM] Suppressed notification — user is viewing conversation $convId');
+      return;
+    }
+
     // Show local notification on Android (iOS handles it natively)
     if (Platform.isAndroid) {
       _localNotifications?.show(