fix(ws): only process unread notifications and handle multiple payload formats

Previously, the notification handler would process all notifications regardless of read status, and only accepted `extra_data` from the payload. Now it:
- Only calls systemNotificationService and increments unread count for unread notifications
- Falls back to `payload.extra` or `payload.data` when `extra_data` is not present

src/stores/message/services/WSMessageHandler.ts

@@ -131,9 +131,10 @@ export class WSMessageHandler implements IWSMessageHandler {
 
     // 监听系统通知，实时更新系统未读数
     wsService.on('notification', (message: WSNotificationMessage) => {
-      if (!message.is_read) {
-        this.incrementSystemUnread();
+      if (message.is_read) {
+        return;
       }
+      this.incrementSystemUnread();
       if (message.created_at) {
         const store = useMessageStore.getState();
         const currentLast = store.lastSystemMessageAt;