✅ test(users): improve test isolation for auth middleware

- update auth middleware mock comment to clarify factory function usage
- add auth middleware mock reset in beforeEach to ensure test independence

src/server/api/__integration_tests__/users.integration.test.ts

@@ -21,7 +21,7 @@ vi.mock('../../modules/users/user.service', () => ({
   }))
 }));
 
-// Mock 认证中间件
+// Mock 认证中间件 - 使用工厂函数确保每个测试有独立的mock实例
 vi.mock('../../middleware/auth.middleware', () => ({
   authMiddleware: vi.fn().mockImplementation((_c, next) => next())
 }));
@@ -50,6 +50,10 @@ describe('Users API Integration Tests', () => {
   beforeEach(async () => {
     vi.clearAllMocks();
 
+    // 重置认证中间件mock
+    const { authMiddleware } = await import('../../middleware/auth.middleware');
+    vi.mocked(authMiddleware).mockImplementation((_c: any, next: any) => next());
+
     // 动态导入用户路由
     const userRoutes = await import('../users/index');