build(config): update bundle identifier and add signing plugin

feat(notification): improve JPush integration and message sync reliability

- Update iOS bundle identifier to `cn.qczlit.weiyou`
- Add `withSigning` Expo plugin
- Enhance `withJPush` plugin with improved Swift AppDelegate injection logic
- Update JPush default channel to `developer-default`
- Optimize `MessageSyncService` to prevent race conditions in unread count updates
- Implement promise deduplication for `fetchUnreadCount` to prevent redundant network requests
- Add `setConversationsWithUnread` to `useMessageStore` for atomic state updates of conversations and unread counts

src/services/notification/jpushService.ts

@@ -26,7 +26,7 @@ try {
     const Constants = require('expo-constants').default;
     const extra = Constants?.expoConfig?.extra || Constants?.extra || {};
     jpushAppKey = extra.jpushAppKey || '';
-    jpushChannel = extra.jpushChannel || 'withyou-default';
+    jpushChannel = extra.jpushChannel || 'developer-default';
   } else {
     console.warn('[JPush] native module not linked, skipping');
   }