feat(ui): add floating menu for video selection

Implement floating button that toggles a menu with video options
Add styling for floating elements and handle click interactions
Update video switching logic to prevent unintended transitions

index.html

@@ -43,6 +43,18 @@
             <p id="transcript"></p>
         </div>
 
+        <!-- 悬浮球 -->
+        <div id="floating-button">
+            <i class="fas fa-bars"></i>
+        </div>
+
+        <!-- 悬浮菜单 -->
+        <div id="menu-container" class="hidden">
+            <button class="menu-item" data-video="视频资源/jimeng-2025-07-16-4437-比耶，然后微笑着优雅的左右摇晃.mp4">Pose</button>
+            <button class="menu-item" data-video="视频资源/生成加油视频.mp4">Cheer</button>
+            <button class="menu-item" data-video="视频资源/生成跳舞视频.mp4">Dance</button>
+        </div>
+
         <!-- 底部麦克风和链接 -->
         <footer class="bottom-bar">
             <button class="mic-button" id="mic-button" aria-label="Start Listening">