QR 생성 로직 수정

src/main/java/com/project/growfit/domain/User/repository/ChildRepository.java

@@ -2,6 +2,7 @@
 
 import com.project.growfit.domain.User.entity.Child;
 import com.project.growfit.domain.User.entity.Parent;
+import java.util.List;
 import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
@@ -18,4 +19,6 @@ public interface ChildRepository extends JpaRepository<Child, Long> {
 
     boolean existsByCodeNumberAndLoginId(String code, String login_id);
     boolean existsByCodeNumber(String code);
+
+    List<Child> findAllByParentOrderByCreatedAtDesc(Parent parent);
 }

src/main/java/com/project/growfit/domain/User/service/impl/AuthParentServiceImpl.java

@@ -65,7 +65,7 @@ public ChildQrCodeResponseDto createQR() throws WriterException {
         int height = 200;
         String uniqueCode = UUID.randomUUID().toString();
 
-        Child child = authenticatedProvider.getAuthenticatedChild();
+        Child child = authenticatedProvider.getAuthenticatedChildForRegistration();
         Long id = child.getId();
 
         log.info("[createQR] QR 코드 생성 요청: user_id={}", parent.getId());

src/main/java/com/project/growfit/global/auth/service/AuthenticatedUserProvider.java

@@ -7,6 +7,7 @@
 import com.project.growfit.global.auth.dto.CustomUserDetails;
 import com.project.growfit.global.exception.BusinessException;
 import com.project.growfit.global.exception.ErrorCode;
+import java.util.List;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.context.SecurityContextHolder;
@@ -41,6 +42,26 @@ public Child getAuthenticatedChild() {
         };
     }
 
+    public Child getAuthenticatedChildForRegistration() {
+        CustomUserDetails user = getCurrentUser();
+        if (user == null) {
+            throw new BusinessException(ErrorCode.UNAUTHORIZED_CHILD); // 인증되지 않은 사용자
+        }
+        return switch (user.getRole()) {
+            case "ROLE_CHILD" -> getChildByLoginId(user.getUserId());
+            case "ROLE_PARENT" -> {
+                Parent parent = getParentByEmail(user.getEmail());
+                List<Child> children = childRepository.findAllByParentOrderByCreatedAtDesc(parent);
+
+                if (children.isEmpty()) {
+                    throw new BusinessException(ErrorCode.CHILD_NOT_FOUND);
+                }
+                yield children.get(0);  // 가장 최근에 생성된 자녀
+            }
+            default -> throw new BusinessException(ErrorCode.FORBIDDEN_ACCESS);
+        };
+    }
+
     private CustomUserDetails getCurrentUser() {
         Authentication auth = SecurityContextHolder.getContext().getAuthentication();
         if (auth == null || !auth.isAuthenticated()) {