refactor(RegisterPage): 使用 VanCheckbox 替换原生 checkbox

为了提高 UI 一致性和用户体验，将注册页面的原生 checkbox 替换为 Vant 的 VanCheckbox 组件。同时更新了相关样式和属性配置。

@@ -26,6 +26,7 @@ declare module 'vue' {
     SummerCampCard: typeof import('./components/ui/SummerCampCard.vue')['default']
     TermsContent: typeof import('./components/ui/TermsContent.vue')['default']
     TermsPopup: typeof import('./components/ui/TermsPopup.vue')['default']
+    VanCheckbox: typeof import('vant/es')['Checkbox']
     VanDatePicker: typeof import('vant/es')['DatePicker']
     VanIcon: typeof import('vant/es')['Icon']
     VanList: typeof import('vant/es')['List']

@@ -80,15 +80,14 @@
           </div>
 
           <div class="flex items-center">
-            <input
+            <van-checkbox
               id="agreeTerms"
               v-model="formData.agreeTerms"
-              type="checkbox"
-              class="h-4 w-4 text-green-600 focus:ring-green-500 border-gray-300 rounded"
-            />
-            <label for="agreeTerms" class="ml-2 block text-sm text-gray-700">
-              我已阅读并同意 <a href="#" class="text-green-600 hover:text-green-500" @click.prevent="openTerms">用户协议</a> 和 <a href="#" class="text-green-600 hover:text-green-500" @click.prevent="openPrivacy">隐私政策</a>
-            </label>
+              shape="square"
+              checked-color="#4caf50"
+              class="scale-90"
+              icon-size="18px"
+            ><span class="text-sm">我已阅读并同意 <a href="#" class="text-green-600 hover:text-green-500" @click.prevent="openTerms">用户协议</a> 和 <a href="#" class="text-green-600 hover:text-green-500" @click.prevent="openPrivacy">隐私政策</a></span></van-checkbox>
           </div>
 
           <div>
@@ -244,3 +243,5 @@ const handleSubmit = async () => {
   }
 }
 </script>
+
+import { Checkbox as VanCheckbox } from 'vant'