feat: add context menu to conversations screen and simplify manage network UI component

lib/features/messaging/presentation/screens/conversations_screen.dart

@@ -200,18 +200,48 @@ class _ConversationsScreenState extends ConsumerState<ConversationsScreen> {
             ),
           ),
           const SizedBox(width: 8),
-          // Three dots menu (outside the search box)
-          GestureDetector(
-            onTap: () {},
-            behavior: HitTestBehavior.opaque,
-            child: const Padding(
-              padding: EdgeInsets.all(4),
-              child: Icon(
-                Icons.more_horiz,
-                size: 22,
-                color: AppColors.primaryDark,
-              ),
+          // Three dots menu
+          PopupMenuButton<String>(
+            icon: const Icon(
+              Icons.more_horiz,
+              size: 22,
+              color: AppColors.primaryDark,
             ),
+            padding: EdgeInsets.zero,
+            onSelected: (value) {
+              switch (value) {
+                case 'mark_all_read':
+                  final conversations =
+                      ref.read(messagingProvider).conversations;
+                  for (final c in conversations) {
+                    if (c.unreadCount > 0) {
+                      ref
+                          .read(messagingProvider.notifier)
+                          .markAsRead(c.id);
+                    }
+                  }
+                  ScaffoldMessenger.of(context).showSnackBar(
+                    const SnackBar(
+                        content: Text('All conversations marked as read')),
+                  );
+                  break;
+                case 'refresh':
+                  ref
+                      .read(messagingProvider.notifier)
+                      .loadConversations();
+                  break;
+              }
+            },
+            itemBuilder: (_) => const [
+              PopupMenuItem(
+                value: 'mark_all_read',
+                child: Text('Mark all as read'),
+              ),
+              PopupMenuItem(
+                value: 'refresh',
+                child: Text('Refresh'),
+              ),
+            ],
           ),
         ],
       ),