전체적인 시스템 추가.

lib/plan_page_detail.dart

@@ -4,36 +4,7 @@ import 'dart:convert';
 import 'main.dart';
 import 'youtube_player_page.dart'; // YoutubePlayerPage import
 import 'common/widgets/custom_bottom_nav_bar.dart';
-
-// PlanDetailItem 클래스 (이전과 동일)
-class PlanDetailItem {
-  final String lessonId;
-  final String lessonTag;
-  final String lessonUrl;
-  final String thumbnail;
-  final String lessonName;
-  final String lessonDescription;
-
-  PlanDetailItem({
-    required this.lessonId,
-    required this.lessonTag,
-    required this.lessonUrl,
-    required this.thumbnail,
-    required this.lessonName,
-    required this.lessonDescription,
-  });
-
-  factory PlanDetailItem.fromJson(Map<String, dynamic> json) {
-    return PlanDetailItem(
-      lessonId: json['casestudy lesson id'] ?? 'ID 없음',
-      lessonTag: json['lesson tag'] ?? '태그 없음',
-      lessonUrl: json['lesson url'] ?? 'URL 없음',
-      thumbnail: json['thumbnail'] ?? '',
-      lessonName: json['lesson_name'] ?? '이름 없음',
-      lessonDescription: json['lesson_description'] ?? '설명 없음',
-    );
-  }
-}
+import 'common/data/plan_detail_item.dart';
 
 class PlanPageDetail extends StatefulWidget {
   const PlanPageDetail({