fix: 刷新页面后恢复滑动进度，防止重复 swipe

服务端 GET room 返回 swipeCounts，前端据此恢复 currentIndex、
swipeHistory 和引导状态；swipe API 增加幂等性检查，跳过已滑过的卡片。

src/app/room/[id]/page.tsx

@@ -15,7 +15,7 @@ export default function RoomPage() {
   const [joined, setJoined] = useState(false);
 
   const {
-    userCount, match, matchType, matchLikes, likeCounts, restaurants, mutate,
+    userCount, match, matchType, matchLikes, likeCounts, swipeCounts, restaurants, mutate,
   } = useRoomPolling(roomId);
 
   useEffect(() => {
@@ -34,6 +34,7 @@ export default function RoomPage() {
     await mutate();
   }, [roomId, mutate]);
 
+  const initialIndex = swipeCounts[userId] ?? 0;
   const ready = joined && userId && restaurants.length > 0;
 
   if (!ready) {
@@ -52,6 +53,7 @@ export default function RoomPage() {
         restaurants={restaurants}
         roomId={roomId}
         userId={userId}
+        initialIndex={initialIndex}
         matchedRestaurantId={match}
         matchType={matchType}
         matchLikes={matchLikes}