feat: 新用户滑动引导，首次进入展示手势提示

- 首张卡片叠加半透明引导层，左滑不想去/右滑想去动画提示
- 支持点击消失、拖拽消失、3秒自动消失
- localStorage 记录标记，每个用户只展示一次
- 修复 React Strict Mode 下 effect 双执行导致引导不显示的问题

src/components/SwipeDeck.tsx

@@ -5,6 +5,7 @@ import { AnimatePresence, motion } from "framer-motion";
 import SwipeableCard from "./SwipeableCard";
 import ActionButtons from "./ActionButtons";
 import MatchResult from "./MatchResult";
+import SwipeGuide from "./SwipeGuide";
 import { Restaurant, SwipeDirection, MatchType } from "@/types";
 import { Heart } from "lucide-react";
 
@@ -36,6 +37,7 @@ export default function SwipeDeck({
   const [localMatchId, setLocalMatchId] = useState<string | null>(null);
   const [resetting, setResetting] = useState(false);
   const [bubble, setBubble] = useState("");
+  const [guideVisible, setGuideVisible] = useState(true);
   const swipeFnRef = useRef<((direction: SwipeDirection) => void) | null>(null);
   const swipingRef = useRef(false);
   const prevLikeCounts = useRef<Record<string, number>>({});
@@ -97,6 +99,7 @@ export default function SwipeDeck({
       if (!current) return;
 
       swipingRef.current = false;
+      if (guideVisible) setGuideVisible(false);
 
       const action = direction === "right" ? "like" : "nope";
       sendSwipe(current.id, action);
@@ -163,6 +166,9 @@ export default function SwipeDeck({
 
       <div className="relative flex flex-1 items-center justify-center px-4">
         <div className="relative h-[70vh] w-full max-w-sm">
+          {currentIndex === 0 && !resolvedMatchId && guideVisible && (
+            <SwipeGuide onDismiss={() => setGuideVisible(false)} />
+          )}
           {!resolvedMatchId && (
             <AnimatePresence>
               {restaurants.map((restaurant, index) => {