fix(frontend): 修复DataTable无限循环和i18n邮箱解析错误

- 修复DataTable组件watch监听actionsExpanded导致的无限循环卡死问题
- 为AccountsView和UsersView添加actionsCount属性启用操作列展开功能
- 修复i18n翻译中邮箱地址的@符号未转义导致的编译错误

frontend/src/views/admin/AccountsView.vue

@@ -165,7 +165,7 @@
         </div>
       </div>
 
-      <DataTable :columns="columns" :data="accounts" :loading="loading">
+      <DataTable :columns="columns" :data="accounts" :loading="loading" :actions-count="6">
           <template #cell-select="{ row }">
             <input
               type="checkbox"

frontend/src/views/admin/UsersView.vue

@@ -85,7 +85,7 @@
 
       <!-- Users Table -->
       <template #table>
-        <DataTable :columns="columns" :data="users" :loading="loading">
+        <DataTable :columns="columns" :data="users" :loading="loading" :actions-count="7">
           <template #cell-email="{ value }">
             <div class="flex items-center gap-2">
               <div