feat(debug): add preview toggles and auto-close ads

- 기록/통계 탭에 디버그 토글 배너 추가 및 테스트 데이터 주입 로직 상태화\n- 리스트 공유 화면에 디버그 프리뷰 토글, 광고 관문, 디버그 전송 흐름 반영\n- 모의 전면 광고는 대기 시간 종료 시 자동 완료되도록 변경\n- AGENTS.md에 코멘트는 한국어로 작성 규칙 명시\n\n테스트: flutter analyze; flutter test

lib/presentation/pages/calendar/calendar_screen.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:table_calendar/table_calendar.dart';
@@ -6,10 +7,12 @@ import '../../../core/constants/app_typography.dart';
 import '../../../domain/entities/recommendation_record.dart';
 import '../../../domain/entities/visit_record.dart';
 import '../../providers/recommendation_provider.dart';
+import '../../providers/debug_test_data_provider.dart';
 import '../../providers/visit_provider.dart';
 import 'widgets/visit_record_card.dart';
 import 'widgets/recommendation_record_card.dart';
 import 'widgets/visit_statistics.dart';
+import 'widgets/debug_test_data_banner.dart';
 
 class CalendarScreen extends ConsumerStatefulWidget {
   const CalendarScreen({super.key});
@@ -32,6 +35,11 @@ class _CalendarScreenState extends ConsumerState<CalendarScreen>
     _selectedDay = DateTime.now();
     _focusedDay = DateTime.now();
     _tabController = TabController(length: 2, vsync: this);
+    if (kDebugMode) {
+      Future.microtask(
+        () => ref.read(debugTestDataNotifierProvider.notifier).initialize(),
+      );
+    }
   }
 
   @override
@@ -100,6 +108,10 @@ class _CalendarScreenState extends ConsumerState<CalendarScreen>
 
         return Column(
           children: [
+            if (kDebugMode)
+              const DebugTestDataBanner(
+                margin: EdgeInsets.fromLTRB(16, 16, 16, 8),
+              ),
             // 캘린더
             Card(
               margin: const EdgeInsets.all(16),