docs: 完善API文档，添加验证码登录功能说明

- 新增验证码登录接口文档 (POST /auth/verification-code-login)
- 新增发送登录验证码接口文档 (POST /auth/send-login-verification-code)
- 更新接口列表和数量统计 (21个 -> 23个接口)
- 添加验证码登录测试场景和cURL示例
- 完善错误码说明和响应格式
- 确保文档与当前实现完全一致

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

@@ -47,7 +47,7 @@ export interface VerificationEmailOptions {
   /** 用户昵称 */
   nickname?: string;
   /** 验证码用途 */
-  purpose: 'email_verification' | 'password_reset';
+  purpose: 'email_verification' | 'password_reset' | 'login_verification';
 }
 
 /**
@@ -167,9 +167,15 @@ export class EmailService {
     if (purpose === 'email_verification') {
       subject = '【Whale Town】邮箱验证码';
       template = this.getEmailVerificationTemplate(code, nickname);
-    } else {
+    } else if (purpose === 'password_reset') {
       subject = '【Whale Town】密码重置验证码';
       template = this.getPasswordResetTemplate(code, nickname);
+    } else if (purpose === 'login_verification') {
+      subject = '【Whale Town】登录验证码';
+      template = this.getPasswordResetTemplate(code, nickname); // 复用密码重置模板
+    } else {
+      subject = '【Whale Town】验证码';
+      template = this.getEmailVerificationTemplate(code, nickname);
     }
 
     return await this.sendEmail({