feat(animation): Act 기반 몬스터 사이즈 시스템 추가

- Act 진행에 따른 몬스터 사이즈 확률 조정
- 보스: Act별 고정 사이즈 (소/중/대)
- 일반/엘리트: Act별 확률 랜덤
- TaskInfo에 monsterSize 필드 추가
- 애니메이션 패널에서 Act 기반 사이즈 사용

lib/src/core/engine/act_progression_service.dart

@@ -1,6 +1,7 @@
 import 'dart:math' as math;
 
 import 'package:asciineverdie/data/game_text_l10n.dart' as l10n;
+import 'package:asciineverdie/src/core/animation/monster_size.dart';
 import 'package:asciineverdie/src/core/engine/combat_calculator.dart';
 import 'package:asciineverdie/src/core/model/combat_state.dart';
 import 'package:asciineverdie/src/core/model/combat_stats.dart';
@@ -253,6 +254,7 @@ class ActProgressionService {
         monsterPart: '*', // 특수 전리품
         monsterLevel: glitchGod.level,
         monsterGrade: MonsterGrade.boss, // 최종 보스는 항상 boss 등급
+        monsterSize: MonsterSize.large, // 최종 보스는 항상 대형
       ),
       currentCombat: combatState,
     );

lib/src/core/engine/progress_service.dart

@@ -1,6 +1,7 @@
 import 'dart:math' as math;
 
 import 'package:asciineverdie/data/game_text_l10n.dart' as l10n;
+import 'package:asciineverdie/src/core/animation/monster_size.dart';
 import 'package:asciineverdie/src/core/engine/act_progression_service.dart';
 import 'package:asciineverdie/src/core/engine/combat_calculator.dart';
 import 'package:asciineverdie/src/core/engine/combat_tick_service.dart';
@@ -585,6 +586,7 @@ class ProgressService {
           monsterPart: '*', // Boss는 WinItem 드랍
           monsterLevel: actBoss.monsterStats.level,
           monsterGrade: MonsterGrade.boss,
+          monsterSize: getBossSizeForAct(state.progress.plotStageCount),
         ),
         currentCombat: actBoss,
       );
@@ -673,6 +675,13 @@ class ProgressService {
       durationMillis,
     );
 
+    // 몬스터 사이즈 결정 (Act 기반, Phase 13)
+    final monsterSize = getMonsterSizeForAct(
+      plotStageCount: state.progress.plotStageCount,
+      grade: monsterResult.grade,
+      rng: state.rng,
+    );
+
     progress = taskResult.progress.copyWith(
       currentTask: TaskInfo(
         caption: taskResult.caption,
@@ -681,6 +690,7 @@ class ProgressService {
         monsterPart: monsterResult.part,
         monsterLevel: effectiveMonsterLevel,
         monsterGrade: monsterResult.grade,
+        monsterSize: monsterSize,
       ),
       currentCombat: combatState,
     );