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/features/shorts/components/ShortSlide.jsx

@@ -33,7 +33,7 @@ export function ShortSlide({ video, active, followed, onToggleFollow, onOpenComm
           <div className="short-player-wrap">
             <div className="short-slide-player">
               {src
-                ? <VideoPlayer src={src} poster={video.image} autoPlay={active} onProgress={(position, duration, flush) => reportWatchProgress(video.preview?.id, position, duration, 'shorts', flush)} />
+                ? <VideoPlayer src={src} poster={video.image} autoPlay={active} soundHint={locale.soundHint} onProgress={(position, duration, flush) => reportWatchProgress(video.preview?.id, position, duration, 'shorts', flush)} />
                 : <div className="short-slide-placeholder"><img src={video.image} alt={video.title} /><span>{video.title}</span></div>}
             </div>
           </div>