refactor(engine): 서비스 로직 정리

- ArenaService, PotionService, ProgressService 개선
- ResurrectionService, SkillService 정리

lib/src/core/engine/skill_service.dart

@@ -446,10 +446,12 @@ class SkillService {
 
     // ATK 증가량 기준 정렬
     buffSkills.sort((a, b) {
-      final aValue = (a.buff?.atkModifier ?? 0) +
+      final aValue =
+          (a.buff?.atkModifier ?? 0) +
           (a.buff?.defModifier ?? 0) * 0.5 +
           (a.buff?.criRateModifier ?? 0) * 0.3;
-      final bValue = (b.buff?.atkModifier ?? 0) +
+      final bValue =
+          (b.buff?.atkModifier ?? 0) +
           (b.buff?.defModifier ?? 0) * 0.5 +
           (b.buff?.criRateModifier ?? 0) * 0.3;
       return bValue.compareTo(aValue);
@@ -470,9 +472,11 @@ class SkillService {
 
     // 디버프 효과 크기 기준 정렬 (음수 값이므로 절대값으로 비교)
     debuffSkills.sort((a, b) {
-      final aValue = (a.buff?.atkModifier ?? 0).abs() +
+      final aValue =
+          (a.buff?.atkModifier ?? 0).abs() +
           (a.buff?.defModifier ?? 0).abs() * 0.5;
-      final bValue = (b.buff?.atkModifier ?? 0).abs() +
+      final bValue =
+          (b.buff?.atkModifier ?? 0).abs() +
           (b.buff?.defModifier ?? 0).abs() * 0.5;
       return bValue.compareTo(aValue);
     });