[fix] AppService의 created_at을 사용하는 로직이 있어 수정 (#401)

src/main/java/org/sopt/app/domain/entity/AppService.java

@@ -9,7 +9,7 @@
 @Builder
 @AllArgsConstructor
 @NoArgsConstructor(access = AccessLevel.PROTECTED)
-public class AppService{
+public class AppService extends BaseEntity {
 
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)