feat(user): 新增邮箱验证码发送接口与校验

- 拆分验证码发送逻辑至独立接口 /sendVerifyMail
- 注册时增加验证码校验与 VERIFY_CODE_ERROR 错误码
- 新增 SendMailDTO 封装邮箱地址参数

src/main/java/com/yolo/keyborad/controller/UserController.java

@@ -86,4 +86,12 @@ public class UserController {
         userService.userRegister(userRegisterDTO);
         return ResultUtils.success(true);
     }
+
+    @PostMapping("/sendVerifyMail")
+    @Operation(summary = "发送验证码",description = "发送验证码接口")
+    public BaseResponse<Boolean> sendVerifyMail(@RequestBody UserRegisterDTO userRegisterDTO) {
+        userService.sendVerifyMail(userRegisterDTO);
+        return ResultUtils.success(true);
+    }
+
 }