feat(user): 新增邮箱注册与验证码发送功能

- 新增 UserRegisterDTO 及 /user/register 接口
- 集成 MailerSend，异步发送 6 位验证码邮件
- 添加 RedisUtil 缓存验证码 10 分钟
- 补充 SEND_MAIL_FAILED、CONFIRM_PASSWORD_NOT_MATCH 错误码
- 关闭 Spring Security CSRF 与表单登录，放行 /user/register
- AppleService 移除 @AllArgsConstructor，改用 @Resource 注入

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

@@ -7,6 +7,7 @@ import com.yolo.keyborad.common.ResultUtils;
 import com.yolo.keyborad.model.dto.AppleLoginReq;
 import com.yolo.keyborad.model.dto.user.KeyboardUserReq;
 import com.yolo.keyborad.model.dto.user.UserLoginDTO;
+import com.yolo.keyborad.model.dto.user.UserRegisterDTO;
 import com.yolo.keyborad.model.entity.KeyboardUser;
 import com.yolo.keyborad.model.vo.user.KeyboardUserInfoRespVO;
 import com.yolo.keyborad.model.vo.user.KeyboardUserRespVO;
@@ -78,4 +79,11 @@ public class UserController {
         KeyboardUser keyboardUser = userService.getById(loginId);
         return ResultUtils.success(BeanUtil.copyProperties(keyboardUser, KeyboardUserInfoRespVO.class));
     }
+
+    @PostMapping("/register")
+    @Operation(summary = "用户注册",description = "用户注册接口")
+    public BaseResponse<Boolean> register(@RequestBody UserRegisterDTO  userRegisterDTO) {
+        userService.userRegister(userRegisterDTO);
+        return ResultUtils.success(true);
+    }
 }