feat(core): 엔진, 모델, 애니메이션 개선

- ProgressService 로직 개선
- CombatCalculator 업데이트
- GameState, MonsterCombatStats 확장
- CanvasBattleComposer 개선

lib/src/core/model/game_state.dart

@@ -475,7 +475,8 @@ class Inventory {
   final int gold;
   final List<InventoryEntry> items;
 
-  factory Inventory.empty() => const Inventory(gold: 0, items: []);
+  /// 초기 골드 1000 지급 (캐릭터 생성 시)
+  factory Inventory.empty() => const Inventory(gold: 1000, items: []);
 
   Inventory copyWith({int? gold, List<InventoryEntry>? items}) {
     return Inventory(gold: gold ?? this.gold, items: items ?? this.items);
@@ -800,6 +801,7 @@ class ProgressState {
     this.deathCount = 0,
     this.finalBossState = FinalBossState.notSpawned,
     this.pendingActCompletion = false,
+    this.bossLevelingEndTime,
   });
 
   final ProgressBarState task;
@@ -835,6 +837,10 @@ class ProgressState {
   /// Act Boss 처치 대기 중 여부 (처치 후 시네마틱 재생 트리거)
   final bool pendingActCompletion;
 
+  /// 보스 사망 후 레벨링 모드 종료 시간 (milliseconds since epoch)
+  /// null이면 레벨링 모드 아님, 값이 있으면 해당 시간까지 레벨링
+  final int? bossLevelingEndTime;
+
   factory ProgressState.empty() => ProgressState(
     task: ProgressBarState.empty(),
     quest: ProgressBarState.empty(),
@@ -867,6 +873,8 @@ class ProgressState {
     int? deathCount,
     FinalBossState? finalBossState,
     bool? pendingActCompletion,
+    int? bossLevelingEndTime,
+    bool clearBossLevelingEndTime = false,
   }) {
     return ProgressState(
       task: task ?? this.task,
@@ -885,8 +893,17 @@ class ProgressState {
       deathCount: deathCount ?? this.deathCount,
       finalBossState: finalBossState ?? this.finalBossState,
       pendingActCompletion: pendingActCompletion ?? this.pendingActCompletion,
+      bossLevelingEndTime: clearBossLevelingEndTime
+          ? null
+          : (bossLevelingEndTime ?? this.bossLevelingEndTime),
     );
   }
+
+  /// 현재 레벨링 모드인지 확인
+  bool get isInBossLevelingMode {
+    if (bossLevelingEndTime == null) return false;
+    return DateTime.now().millisecondsSinceEpoch < bossLevelingEndTime!;
+  }
 }
 
 class QueueEntry {

lib/src/core/model/monster_combat_stats.dart

@@ -131,15 +131,29 @@ class MonsterCombatStats {
   /// [level] 몬스터 레벨 (원본 데이터 기준)
   /// [speedType] 공격 속도 타입 (기본: normal)
   /// [monsterType] 몬스터 타입 (기본: normal)
+  /// [plotStageCount] 현재 Act (1=Prologue, 2=Act I, 3=Act II, ...)
   factory MonsterCombatStats.fromLevel({
     required String name,
     required int level,
     MonsterSpeedType speedType = MonsterSpeedType.normal,
     MonsterType monsterType = MonsterType.normal,
+    int plotStageCount = 1,
   }) {
     // balance_constants.dart의 MonsterBaseStats 사용
     final baseStats = MonsterBaseStats.generate(level, monsterType);
 
+    // Act II 이후 (plotStageCount >= 3) HP 10% 상승
+    final hpMultiplier = plotStageCount >= 3 ? 1.1 : 1.0;
+    final adjustedHp = (baseStats.hp * hpMultiplier).round();
+
+    // Act별 경험치 배율 (후반부 레벨업 가속)
+    final expMultiplier = switch (plotStageCount) {
+      5 => 1.3, // Act IV: 30% 보너스
+      6 => 1.8, // Act V: 80% 보너스 (보스전 대비)
+      _ => 1.0, // 기본
+    };
+    final adjustedExp = (baseStats.exp * expMultiplier).round();
+
     // 크리티컬 확률: 레벨에 따라 천천히 증가 (0.02 ~ 0.3)
     final criRate = (0.02 + level * 0.003).clamp(0.02, 0.3);
 
@@ -164,14 +178,14 @@ class MonsterCombatStats {
       level: level,
       atk: baseStats.atk,
       def: baseStats.def,
-      hpMax: baseStats.hp,
-      hpCurrent: baseStats.hp,
+      hpMax: adjustedHp,
+      hpCurrent: adjustedHp,
       criRate: criRate,
       criDamage: criDamage,
       evasion: evasion,
       accuracy: accuracy,
       attackDelayMs: attackDelayMs,
-      expReward: baseStats.exp,
+      expReward: adjustedExp,
     );
   }