feat: implement message delivery status tracking via socket events and provider state updates

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

@@ -171,6 +171,38 @@ class MessagingNotifier extends StateNotifier<MessagingState> {
       }
     }));
 
+    // Delivered receipts — update single tick → double tick
+    _subscriptions.add(_socket.onMessageDelivered.listen((data) {
+      if (!mounted) return;
+      final convId = data['conversationId'] as String?;
+      final messageId = data['messageId'] as String?;
+      final deliveredAt = data['deliveredAt'] as String?;
+      if (convId == null) return;
+
+      final currentMessages = List<ChatMessage>.from(state.messages[convId] ?? []);
+      bool changed = false;
+
+      final updatedMessages = currentMessages.map((m) {
+        // Update specific message or all sent messages in this conversation
+        if (messageId != null && m.id == messageId && m.status == MessageStatus.sent) {
+          changed = true;
+          return m.copyWith(status: MessageStatus.delivered, deliveredAt: deliveredAt);
+        }
+        // If no specific messageId, mark all sent messages as delivered
+        if (messageId == null && m.senderId == _currentUserId && m.status == MessageStatus.sent) {
+          changed = true;
+          return m.copyWith(status: MessageStatus.delivered, deliveredAt: deliveredAt);
+        }
+        return m;
+      }).toList();
+
+      if (changed) {
+        final newMessages = Map<String, List<ChatMessage>>.from(state.messages)
+          ..[convId] = updatedMessages;
+        state = state.copyWith(messages: newMessages);
+      }
+    }));
+
     // Read receipts — update message ticks and conversation unread count
     _subscriptions.add(_socket.onMessagesRead.listen((data) {
       if (!mounted) return;