refactor: enhance SkinCard and SkinViewer components for improved visuals

- Updated background gradient colors in SkinCard for better contrast.
- Wrapped SkinViewer in a div for consistent styling and layout.
- Adjusted overlay gradient opacity in SkinCard for a subtler effect.
- Increased global light intensity and adjusted camera light in SkinViewer to enhance skin visibility and reduce harsh shadows.

src/components/SkinViewer.tsx

@@ -101,6 +101,10 @@ export default function SkinViewer({
       viewer.background = null; // 透明背景
       viewer.autoRotate = false; // 完全禁用自动旋转
       
+      // 调整光照设置，避免皮肤发黑
+      viewer.globalLight.intensity = 0.8; // 增加环境光强度
+      viewer.cameraLight.intensity = 0.4; // 降低相机光源强度，避免过强的阴影
+      
       // 外部预览时禁用所有动画和旋转
       if (isExternalPreview) {
         viewer.autoRotate = false;