style(auth)：优化auth模块代码规范和测试覆盖

范围：src/business/auth/
- 统一命名规范和注释格式
- 完善文件头部注释和修改记录
- 分离登录和注册业务逻辑到独立服务
- 添加缺失的测试文件（JWT守卫、控制器测试）
- 清理未使用的测试文件
- 优化代码结构和依赖关系

src/business/auth/login.service.spec.ts

@@ -60,18 +60,14 @@ describe('LoginService', () => {
 
     const mockLoginCoreService = {
       login: jest.fn(),
-      register: jest.fn(),
       githubOAuth: jest.fn(),
       sendPasswordResetCode: jest.fn(),
       resetPassword: jest.fn(),
       changePassword: jest.fn(),
-      sendEmailVerification: jest.fn(),
-      verifyEmailCode: jest.fn(),
-      resendEmailVerification: jest.fn(),
       verificationCodeLogin: jest.fn(),
       sendLoginVerificationCode: jest.fn(),
       debugVerificationCode: jest.fn(),
-      deleteUser: jest.fn(),
+      refreshAccessToken: jest.fn(),
       generateTokenPair: jest.fn(),
     };
 
@@ -178,44 +174,6 @@ describe('LoginService', () => {
     });
   });
 
-  describe('register', () => {
-    it('should register successfully with JWT tokens', async () => {
-      loginCoreService.register.mockResolvedValue({
-        user: mockUser,
-        isNewUser: true
-      });
-
-      const result = await service.register({
-        username: 'newuser',
-        password: 'password123',
-        nickname: '新用户',
-        email: 'newuser@example.com',
-        email_verification_code: '123456'
-      });
-
-      expect(result.success).toBe(true);
-      expect(result.data?.user.username).toBe('testuser');
-      expect(result.data?.access_token).toBe(mockTokenPair.access_token);
-      expect(result.data?.is_new_user).toBe(true);
-      expect(loginCoreService.register).toHaveBeenCalled();
-      expect(loginCoreService.generateTokenPair).toHaveBeenCalledWith(mockUser);
-    });
-
-    it('should handle register failure', async () => {
-      loginCoreService.register.mockRejectedValue(new Error('用户名已存在'));
-
-      const result = await service.register({
-        username: 'existinguser',
-        password: 'password123',
-        nickname: '用户'
-      });
-
-      expect(result.success).toBe(false);
-      expect(result.message).toBe('用户名已存在');
-      expect(result.error_code).toBe('REGISTER_FAILED');
-    });
-  });
-
   describe('githubOAuth', () => {
     it('should handle GitHub OAuth successfully', async () => {
       loginCoreService.githubOAuth.mockResolvedValue({
@@ -282,34 +240,6 @@ describe('LoginService', () => {
     });
   });
 
-  describe('sendEmailVerification', () => {
-    it('should handle sendEmailVerification in test mode', async () => {
-      loginCoreService.sendEmailVerification.mockResolvedValue({
-        code: '123456',
-        isTestMode: true
-      });
-
-      const result = await service.sendEmailVerification('test@example.com');
-
-      expect(result.success).toBe(false); // Test mode returns false
-      expect(result.data?.verification_code).toBe('123456');
-      expect(result.data?.is_test_mode).toBe(true);
-      expect(loginCoreService.sendEmailVerification).toHaveBeenCalledWith('test@example.com');
-    });
-  });
-
-  describe('verifyEmailCode', () => {
-    it('should handle verifyEmailCode successfully', async () => {
-      loginCoreService.verifyEmailCode.mockResolvedValue(true);
-
-      const result = await service.verifyEmailCode('test@example.com', '123456');
-
-      expect(result.success).toBe(true);
-      expect(result.message).toBe('邮箱验证成功');
-      expect(loginCoreService.verifyEmailCode).toHaveBeenCalledWith('test@example.com', '123456');
-    });
-  });
-
   describe('verificationCodeLogin', () => {
     it('should handle verificationCodeLogin successfully', async () => {
       loginCoreService.verificationCodeLogin.mockResolvedValue({