feat: 移动端沉浸式 Shorts 与播放器/下载徽章体验优化

- 移动端移除底部导航，Shorts 视频改为圆角卡片并适配 iOS 裁剪
- 播放进度条全局贴到视频最底，移动端精简控件（仅播放/全屏）
- 右侧互动栏下移，首页进入播放页增加模糊封面过渡
- 关于页下载入口改为标准 App Store / Google Play 徽章
- 新增自动连播下一集与自动播放被拦截时的开启声音提示

src/shared/components/HeroTransition.jsx

@@ -0,0 +1,48 @@
+// Author: fruit.com.cn
+import { useLayoutEffect, useRef } from 'react';
+
+const DURATION = 420;
+const FADE = 180;
+
+export function HeroTransition({ data, onDone }) {
+  const ref = useRef(null);
+
+  useLayoutEffect(() => {
+    if (!data) return undefined;
+    const node = ref.current;
+    if (!node) return undefined;
+    if (window.matchMedia?.('(prefers-reduced-motion: reduce)').matches) {
+      onDone();
+      return undefined;
+    }
+    const rect = data;
+    const scale = Math.max(window.innerWidth / rect.width, window.innerHeight / rect.height) * 1.04;
+    const tx = (window.innerWidth - rect.width * scale) / 2 - rect.left;
+    const ty = (window.innerHeight - rect.height * scale) / 2 - rect.top;
+    const expand = node.animate(
+      [
+        { transform: 'translate(0, 0) scale(1)', borderRadius: '12px' },
+        { transform: `translate(${tx}px, ${ty}px) scale(${scale})`, borderRadius: '0px' },
+      ],
+      { duration: DURATION, easing: 'cubic-bezier(.2, .7, .3, 1)', fill: 'forwards' },
+    );
+    expand.onfinish = () => {
+      const fade = node.animate([{ opacity: 1 }, { opacity: 0 }], { duration: FADE, fill: 'forwards' });
+      fade.onfinish = onDone;
+    };
+    return () => expand.cancel();
+  }, [data, onDone]);
+
+  if (!data) return null;
+  const rect = data;
+  return (
+    <div
+      ref={ref}
+      className="hero-transition"
+      aria-hidden="true"
+      style={{ left: rect.left, top: rect.top, width: rect.width, height: rect.height }}
+    >
+      {data.src && <img src={data.src} alt="" />}
+    </div>
+  );
+}