fix: 修复proxy_service和account_service中不当的顶层import

- proxy_service.py: 将requests和WhitelistManager改为函数内延迟import，
  避免启动时加载不需要的依赖；移除未使用的get_exit_ip_via_proxy导入
- account_service.py: 移除未使用的func、joinedload、AuditLog、
  user_has_permission顶层导入

web/frontend/src/pages/UsersPage.tsx

@@ -5,7 +5,7 @@ import {
 } from 'antd';
 import { PlusOutlined, EditOutlined, DeleteOutlined, SafetyOutlined } from '@ant-design/icons';
 import { userApi, type UserInfo } from '../api/modules';
-import { getUser, hasPerm } from '../store/auth';
+import { usePermissions } from '../hooks/usePermissions';
 import { getErrorMessage } from '../utils/error';
 
 const ROLE_OPTIONS = [
@@ -50,8 +50,9 @@ export default function UsersPage() {
   const [selectedPerms, setSelectedPerms] = useState<string[]>([]);
   const [useCustom, setUseCustom] = useState(false);
   const [permLoading, setPermLoading] = useState(false);
+  const { can } = usePermissions();
 
-  const canAssignPerm = hasPerm(getUser(), 'user:assign_permissions');
+  const canAssignPerm = can('user:assign_permissions');
 
   const loadUsers = async () => {
     setLoading(true);