fix: user domain ID 값 원상복구

Author: nickhealthy

src/main/java/app/dearobjet/backend/domain/user/entity/User.java

@@ -16,7 +16,7 @@ public class User extends BaseTimeEntity {
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     @Column(name = "user_id")
-    private Long id;
+    private Long userId;
 
     @Column(nullable = false, unique = true)
     private String email;