修复Settings.vue中userApi未定义的问题，正确导入setAdmin函数

frontend/src/views/Settings.vue

@@ -2618,6 +2618,7 @@ import {
   getAllUsers,
   updateUserDepartment,
   deleteUser,
+  setAdmin,
   type User
 } from '@/api/user'
 import {
@@ -4494,7 +4495,7 @@ const deleteUserFromCard = async (user: User) => {
 const toggleUserAdmin = async (user: User) => {
   try {
     const newAdminStatus = user.isAdmin === 1 ? 0 : 1
-    await userApi.setAdmin(user.id!, newAdminStatus)
+    await setAdmin(user.id!, newAdminStatus)
     message.success(newAdminStatus === 1 ? '已设置为管理员' : '已取消管理员身份')
     await loadDepartmentUsers()
   } catch (error) {