fix(profile): 替换默认头像链接并优化用户名修改提示

将默认头像链接更改为公司CDN地址，提升加载速度。使用`showToast`替换`alert`，优化用户体验。

 <!--
  * @Date: 2025-03-24 13:04:21
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-03-26 00:46:59
+ * @LastEditTime: 2025-03-26 13:27:45
  * @FilePath: /mlaj/src/views/profile/settings/AvatarSettingPage.vue
  * @Description: 修改头像页面
 -->
@@ -18,7 +18,7 @@
                 <van-image
                   round
                   :src="
-                    userAvatar || 'https://fastly.jsdelivr.net/npm/@vant/assets/cat.jpeg'
+                    userAvatar || 'https://cdn.ipadbiz.cn/mlaj/images/icon_1.jpeg'
                   "
                   alt="用户头像"
                   class="rounded-full border-4 border-white shadow-lg"

 <!--
  * @Date: 2025-03-24 13:04:21
  * @LastEditors: hookehuyr hookehuyr@gmail.com
- * @LastEditTime: 2025-03-26 13:03:27
+ * @LastEditTime: 2025-03-26 13:42:45
  * @FilePath: /mlaj/src/views/profile/settings/UsernameSettingPage.vue
  * @Description: 修改用户名页面
 -->
@@ -43,7 +43,7 @@ import { ref, onMounted } from 'vue';
 import AppLayout from '@/components/layout/AppLayout.vue';
 import FrostedGlass from '@/components/ui/FrostedGlass.vue';
 import { getUserInfoAPI, updateUserInfoAPI } from '@/api/users';
-
+import { showToast } from 'vant';
 import { useTitle } from '@vueuse/core';
 
 const $route = useRoute();
@@ -67,18 +67,18 @@ onMounted(async () => {
 // 处理用户名修改
 const handleUsernameChange = async () => {
   if (!username.value) {
-    alert('请输入新的用户名');
+    showToast('请输入新的用户名');
     return;
   }
 
   try {
-    const response = await updateUserInfoAPI({ name: username.value });
-    if (response.data) {
-      alert('用户名修改成功');
+    const { code } = await updateUserInfoAPI({ name: username.value });
+    if (code) {
+      showToast('用户名修改成功');
     }
   } catch (error) {
     console.error('用户名修改失败:', error);
-    alert('用户名修改失败，请重试');
+    showToast('用户名修改失败，请重试');
   }
 };
 </script>