feat(video): add video fit toggle button and update styling

- Add toggle button to switch between 'cover' and 'contain' video fit modes
- Update video background styling for simpler positioning
- Group upload and fit buttons in a flex container

script.js

@@ -7,6 +7,8 @@ document.addEventListener('DOMContentLoaded', function() {
     const micButton = document.getElementById('mic-button');
     const favorabilityBar = document.getElementById('favorability-bar');
 
+    const toggleFitButton = document.getElementById('toggle-fit-button');
+
     // --- 视频上传功能 ---
     videoUploadInput.addEventListener('change', function(event) {
         const file = event.target.files[0];
@@ -27,6 +29,19 @@ document.addEventListener('DOMContentLoaded', function() {
         }
     });
 
+    // --- 视频适应模式切换功能 ---
+    let isFitHeight = false;
+    toggleFitButton.addEventListener('click', function() {
+        isFitHeight = !isFitHeight;
+        if (isFitHeight) {
+            bgVideo.style.objectFit = 'contain';
+            toggleFitButton.textContent = '适应宽度';
+        } else {
+            bgVideo.style.objectFit = 'cover';
+            toggleFitButton.textContent = '适应高度';
+        }
+    });
+
     // --- 麦克风按钮交互和好感度条模拟 ---
     let isListening = false;
     let currentFavorability = 65; // 与 CSS 中的初始宽度保持一致