最近活跃的群聊排最上面，无消息的排最后

server/routes/rooms.js

@@ -21,6 +21,13 @@ router.get('/', authMiddleware, (req, res) => {
     const lastMsg = db.prepare('SELECT text, timestamp FROM messages WHERE room_id = ? ORDER BY id DESC LIMIT 1').get(room.id);
     return { ...room, last_message: lastMsg ? lastMsg.text : '', last_time: lastMsg ? lastMsg.timestamp : '' };
   });
+  // 按最后消息时间排序，最近的在前，无消息的排最后
+  result.sort((a, b) => {
+    if (!a.last_time && !b.last_time) return 0;
+    if (!a.last_time) return 1;
+    if (!b.last_time) return -1;
+    return b.last_time.localeCompare(a.last_time);
+  });
   res.json(result);
 });