fix(AdPage): 添加默认广告图片并在加载失败时显示

当广告图片URL为空时显示默认图片，避免空白页面

 <!--
  * @Date: 2022-09-19 14:11:06
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-09-26 17:20:49
+ * @LastEditTime: 2025-09-28 14:03:53
  * @FilePath: /lls_program/src/pages/AdPage/index.vue
  * @Description: 广告页面
 -->
@@ -36,7 +36,7 @@
     <!-- 背景图片 -->
     <image
       v-show="!imageLoading && !imageLoadError"
-      :src="adImageUrl"
+      :src="adImageUrl || defaultAdImage"
       class="ad-background"
       mode="scaleToFill"
       @tap="handleImageClick"
@@ -75,6 +75,9 @@ import { getMyFamiliesAPI } from "@/api/family";
 import { silentAuth } from "@/utils/authRedirect";
 import "./index.less";
 
+// 默认广告图片
+const defaultAdImage = 'https://cdn.ipadbiz.cn/space_34093/%E5%BC%95%E5%AF%BC%E9%A1%B51_Fu2ZY_Tm6TL1OzbyrqQkeVRAdVfU.jpg?imageMogr2/strip/quality/60';
+
 // 定义响应式数据
 const adImageUrl = ref('');
 const loading = ref(true);