task-51(账号/权限页面): 实现用户删除确认和刷新

新增 user-delete-model.ts 纯模型：deleteConfirmMessage/deleteBlockReason 镜像 Java
deleteUser 约束(不能删自己/超管)、isDeletableUser。users.ts 增 deleteUser DELETE
/api/admin/user/{uid} 并由 unwrap 抛后端 message；UsersPage 删除改走 adapter、二次确认后
刷新列表(超管行直接告警拦截)，不再内联 http.delete、不入 session store。
8 用例全过，371 单测 + build 绿。

admin-frontend-vue/src/pages/account/UsersPage.vue

@@ -1,11 +1,11 @@
 <script setup lang="ts">
 import { onMounted, reactive, ref } from 'vue'
 import { ElMessage, ElMessageBox } from 'element-plus'
-import { http } from '@/api/http'
 import type { AdminUser } from '@/types/admin'
-import { fetchUserList } from '@/api/users'
+import { deleteUser, fetchUserList } from '@/api/users'
 import { createUserFilterState, toUserListParams } from './users-filter'
 import { totalPageCount } from './user-pagination'
+import { deleteBlockReason } from './user-delete-model'
 
 const loading = ref(false)
 const rows = ref<AdminUser[]>([])
@@ -40,9 +40,14 @@ function search() {
 }
 
 async function removeUser(row: AdminUser) {
+  const reason = deleteBlockReason(row)
+  if (reason) {
+    ElMessage.warning(reason)
+    return
+  }
   try {
     await ElMessageBox.confirm(`确定删除用户“${row.username}”吗？`, '删除确认', { type: 'warning' })
-    await http.delete(`/api/admin/user/${row.id}`)
+    await deleteUser(row.id)
     ElMessage.success('删除成功')
     await loadUsers()
   } catch (error) {