refactor(core): 진행 루프, 저장 데이터, 저장 관리자 개선

- ProgressLoop 로직 정리
- SaveData 모델 확장
- SaveManager 개선

lib/src/core/storage/save_manager.dart

@@ -13,19 +13,23 @@ class SaveManager {
 
   /// Save current game state to disk. [fileName] may be absolute or relative.
   /// Returns outcome with error on failure.
-  Future<SaveOutcome> saveState(GameState state, {String? fileName}) {
-    final save = GameSave.fromState(state);
+  Future<SaveOutcome> saveState(
+    GameState state, {
+    String? fileName,
+    bool cheatsEnabled = false,
+  }) {
+    final save = GameSave.fromState(state, cheatsEnabled: cheatsEnabled);
     return _repo.save(save, fileName ?? defaultFileName);
   }
 
   /// Load game state from disk. [fileName] may be absolute (e.g., file picker).
-  /// Returns outcome + optional state.
-  Future<(SaveOutcome, GameState?)> loadState({String? fileName}) async {
+  /// Returns outcome + optional state + cheatsEnabled flag.
+  Future<(SaveOutcome, GameState?, bool)> loadState({String? fileName}) async {
     final (outcome, save) = await _repo.load(fileName ?? defaultFileName);
     if (!outcome.success || save == null) {
-      return (outcome, null);
+      return (outcome, null, false);
     }
-    return (outcome, save.toState());
+    return (outcome, save.toState(), save.cheatsEnabled);
   }
 
   /// 저장 파일 목록 조회