feat: fix backend some error;fix frontend display error

backend/app.js

@@ -20,7 +20,7 @@ app.get('/api/messages', async (req, res) => {
 
   try {
     const [rows] = await db.execute(
-      'SELECT id, sender, subject, body, received_at FROM emails WHERE recipient = ? ORDER BY received_at DESC',
+      'SELECT id, sender, recipient, subject, body, received_at FROM emails WHERE recipient = ? ORDER BY received_at DESC',
       [recipient]
     );
     res.json(rows);