feat(story): Phase 9 스토리/엔딩 시스템 구현

- story_data.dart: 5개 Act 스토리 텍스트 및 ASCII 아트
- story_service.dart: Act 전환/보스 조우/엔딩 이벤트 관리
- cinematic_view.dart: 풀스크린 시네마틱 UI (페이드, 스킵)
- game_play_screen.dart: 레벨 기반 Act 전환 시 시네마틱 재생

lib/src/features/game/game_play_screen.dart

@@ -1,12 +1,15 @@
 import 'package:flutter/material.dart';
 
+import 'package:askiineverdie/data/story_data.dart';
 import 'package:askiineverdie/l10n/app_localizations.dart';
 import 'package:askiineverdie/src/core/animation/ascii_animation_type.dart';
+import 'package:askiineverdie/src/core/engine/story_service.dart';
 import 'package:askiineverdie/src/core/l10n/game_data_l10n.dart';
 import 'package:askiineverdie/src/core/model/game_state.dart';
 import 'package:askiineverdie/src/core/notification/notification_service.dart';
 import 'package:askiineverdie/src/core/util/pq_logic.dart' as pq_logic;
 import 'package:askiineverdie/src/features/game/game_session_controller.dart';
+import 'package:askiineverdie/src/features/game/widgets/cinematic_view.dart';
 import 'package:askiineverdie/src/features/game/widgets/notification_overlay.dart';
 import 'package:askiineverdie/src/features/game/widgets/stats_panel.dart';
 import 'package:askiineverdie/src/features/game/widgets/task_progress_panel.dart';
@@ -30,6 +33,11 @@ class _GamePlayScreenState extends State<GamePlayScreen>
   // Phase 8: 알림 서비스 (Notification Service)
   late final NotificationService _notificationService;
 
+  // Phase 9: 스토리 서비스 (Story Service)
+  late final StoryService _storyService;
+  StoryAct _lastAct = StoryAct.prologue;
+  bool _showingCinematic = false;
+
   // 이전 상태 추적 (레벨업/퀘스트/Act 완료 감지용)
   int _lastLevel = 0;
   int _lastQuestCount = 0;
@@ -41,6 +49,13 @@ class _GamePlayScreenState extends State<GamePlayScreen>
       _specialAnimation = AsciiAnimationType.levelUp;
       _notificationService.showLevelUp(state.traits.level);
       _resetSpecialAnimationAfterFrame();
+
+      // Phase 9: Act 변경 감지 (레벨 기반)
+      final newAct = getActForLevel(state.traits.level);
+      if (newAct != _lastAct && !_showingCinematic) {
+        _lastAct = newAct;
+        _showCinematicForAct(newAct);
+      }
     }
     _lastLevel = state.traits.level;
 
@@ -68,6 +83,25 @@ class _GamePlayScreenState extends State<GamePlayScreen>
     _lastPlotStageCount = state.progress.plotStageCount;
   }
 
+  /// Phase 9: Act 시네마틱 표시 (Show Act Cinematic)
+  Future<void> _showCinematicForAct(StoryAct act) async {
+    if (_showingCinematic) return;
+
+    _showingCinematic = true;
+    // 게임 일시 정지
+    await widget.controller.pause(saveOnStop: false);
+
+    if (mounted) {
+      await showActCinematic(context, act);
+    }
+
+    // 게임 재개
+    if (mounted) {
+      await widget.controller.resume();
+    }
+    _showingCinematic = false;
+  }
+
   void _resetSpecialAnimationAfterFrame() {
     // 다음 프레임에서 리셋 (AsciiAnimationCard가 값을 받은 후)
     WidgetsBinding.instance.addPostFrameCallback((_) {
@@ -83,6 +117,7 @@ class _GamePlayScreenState extends State<GamePlayScreen>
   void initState() {
     super.initState();
     _notificationService = NotificationService();
+    _storyService = StoryService();
     widget.controller.addListener(_onControllerChanged);
     WidgetsBinding.instance.addObserver(this);
 
@@ -92,12 +127,14 @@ class _GamePlayScreenState extends State<GamePlayScreen>
       _lastLevel = state.traits.level;
       _lastQuestCount = state.progress.questCount;
       _lastPlotStageCount = state.progress.plotStageCount;
+      _lastAct = getActForLevel(state.traits.level);
     }
   }
 
   @override
   void dispose() {
     _notificationService.dispose();
+    _storyService.dispose();
     WidgetsBinding.instance.removeObserver(this);
     widget.controller.removeListener(_onControllerChanged);
     super.dispose();