style(PdfViewer): 调整PDF预览组件的背景透明度

 <!--
  * @Date: 2025-01-21
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-10-22 13:42:16
+ * @LastEditTime: 2025-10-22 13:49:33
  * @FilePath: /mlaj/src/components/ui/PdfViewer.vue
  * @Description: PDF预览组件 - 使用pdf-vue3库
 -->
@@ -799,7 +799,7 @@ const applyPinchZoom = (newZoom, centerX, centerY, container) => {
     align-items: center;
     justify-content: center;
     height: 100%;
-    background: rgba(0, 0, 0, 0.7);
+    background: rgba(0, 0, 0, 0.1);
     backdrop-filter: blur(4px);
 }