refactor(model): 모델 및 스토리지 정리

- GameState, GameStatistics, HallOfFame 개선
- MonsterGrade, HallOfFameStorage 정리

lib/src/core/model/game_state.dart

@@ -763,6 +763,7 @@ class ProgressState {
     this.monstersKilled = 0,
     this.deathCount = 0,
     this.finalBossState = FinalBossState.notSpawned,
+    this.pendingActCompletion = false,
   });
 
   final ProgressBarState task;
@@ -795,6 +796,9 @@ class ProgressState {
   /// 최종 보스 상태 (Act V)
   final FinalBossState finalBossState;
 
+  /// Act Boss 처치 대기 중 여부 (처치 후 시네마틱 재생 트리거)
+  final bool pendingActCompletion;
+
   factory ProgressState.empty() => ProgressState(
     task: ProgressBarState.empty(),
     quest: ProgressBarState.empty(),
@@ -826,6 +830,7 @@ class ProgressState {
     int? monstersKilled,
     int? deathCount,
     FinalBossState? finalBossState,
+    bool? pendingActCompletion,
   }) {
     return ProgressState(
       task: task ?? this.task,
@@ -843,6 +848,7 @@ class ProgressState {
       monstersKilled: monstersKilled ?? this.monstersKilled,
       deathCount: deathCount ?? this.deathCount,
       finalBossState: finalBossState ?? this.finalBossState,
+      pendingActCompletion: pendingActCompletion ?? this.pendingActCompletion,
     );
   }
 }