feat: 新增邀请中间页，分享链接带上下文引导新用户加入

src/components/TopNav.tsx

@@ -20,7 +20,7 @@ export default function TopNav({ roomId, userCount }: TopNavProps) {
   }, []);
 
   const handleInvite = useCallback(async () => {
-    const url = window.location.href;
+    const url = `${window.location.origin}/invite/${roomId}`;
     const shareData = {
       title: "别说随便啦，来滑卡片决定吃什么！",
       text: "我建好房间了，快点开链接一起选餐厅，滑中同一家就去吃！",
@@ -42,7 +42,7 @@ export default function TopNav({ roomId, userCount }: TopNavProps) {
     } catch {
       showToast("复制失败，请手动复制链接");
     }
-  }, [showToast]);
+  }, [roomId, showToast]);
 
   return (
     <>