test：添加登录验证码邮件发送测试

为修复的登录验证码邮件模板功能添加专门的测试用例：
- 测试登录验证码邮件发送功能
- 验证邮件模板内容包含正确的登录验证码信息
- 确保邮件主题和内容符合预期

src/core/utils/email/email.service.spec.ts

@@ -221,6 +221,30 @@ describe('EmailService', () => {
       );
     });
 
+    it('应该成功发送登录验证码', async () => {
+      const options: VerificationEmailOptions = {
+        email: 'test@example.com',
+        code: '789012',
+        nickname: '测试用户',
+        purpose: 'login_verification'
+      };
+
+      mockTransporter.sendMail.mockResolvedValue({ messageId: 'test-id' });
+      configService.get.mockReturnValue('"Test Sender" <noreply@test.com>');
+
+      const result = await service.sendVerificationCode(options);
+
+      expect(result.success).toBe(true);
+      expect(result.isTestMode).toBe(false);
+      expect(mockTransporter.sendMail).toHaveBeenCalledWith(
+        expect.objectContaining({
+          to: 'test@example.com',
+          subject: '【Whale Town】登录验证码',
+          text: '您的验证码是：789012，5分钟内有效，请勿泄露给他人。'
+        })
+      );
+    });
+
     it('应该在发送失败时返回false', async () => {
       const options: VerificationEmailOptions = {
         email: 'test@example.com',
@@ -323,6 +347,26 @@ describe('EmailService', () => {
       await service.sendVerificationCode(options);
     });
 
+    it('应该生成包含验证码的登录验证模板', async () => {
+      const options: VerificationEmailOptions = {
+        email: 'test@example.com',
+        code: '789012',
+        nickname: '测试用户',
+        purpose: 'login_verification'
+      };
+
+      mockTransporter.sendMail.mockImplementation((mailOptions: any) => {
+        expect(mailOptions.html).toContain('789012');
+        expect(mailOptions.html).toContain('测试用户');
+        expect(mailOptions.html).toContain('登录验证码');
+        expect(mailOptions.html).toContain('您正在使用验证码登录');
+        expect(mailOptions.html).toContain('🔐');
+        return Promise.resolve({ messageId: 'test-id' });
+      });
+
+      await service.sendVerificationCode(options);
+    });
+
     it('应该生成包含用户昵称的欢迎邮件模板', async () => {
       mockTransporter.sendMail.mockImplementation((mailOptions: any) => {
         expect(mailOptions.html).toContain('测试用户');