feat(iap): persist adsRemoved flag (additive, saveVersion 1)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/data/save_repository.dart

@@ -39,6 +39,9 @@ class SaveRepository {
               false;
       _endlessBest =
           (json['endless'] as Map<String, dynamic>?)?['best'] as int? ?? 0;
+      _adsRemoved =
+          (json['flags'] as Map<String, dynamic>?)?['adsRemoved'] as bool? ??
+              false;
     }
   }
 
@@ -52,16 +55,23 @@ class SaveRepository {
   StreakState _streak = StreakState.initial;
   bool _tutorialDone = false;
   int _endlessBest = 0;
+  bool _adsRemoved = false;
 
   StreakState get streak => _streak;
   bool get tutorialDone => _tutorialDone;
   int get endlessBest => _endlessBest;
+  bool get adsRemoved => _adsRemoved;
 
   Future<void> markTutorialDone() {
     _tutorialDone = true;
     return _flush();
   }
 
+  Future<void> setAdsRemoved(bool value) {
+    _adsRemoved = value;
+    return _flush();
+  }
+
   Future<void> recordEndlessScore(int score) {
     if (score > _endlessBest) _endlessBest = score;
     return _flush();
@@ -130,7 +140,7 @@ class SaveRepository {
             'best': _streak.best,
             'lastYmd': _streak.lastYmd,
           },
-          'flags': {'tutorialDone': _tutorialDone},
+          'flags': {'tutorialDone': _tutorialDone, 'adsRemoved': _adsRemoved},
           'endless': {'best': _endlessBest},
         }),
       );

test/data/save_repository_ads_test.dart

@@ -0,0 +1,26 @@
+import 'package:block_seasons/data/save_repository.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  setUp(() => SharedPreferences.setMockInitialValues({}));
+
+  test('adsRemoved defaults to false and persists across reopen', () async {
+    final repo = await SaveRepository.open();
+    expect(repo.adsRemoved, isFalse);
+    await repo.setAdsRemoved(true);
+    expect(repo.adsRemoved, isTrue);
+
+    final reopened = await SaveRepository.open();
+    expect(reopened.adsRemoved, isTrue);
+  });
+
+  test('legacy save without the ads flag reads as false', () async {
+    SharedPreferences.setMockInitialValues({
+      'save_v1': '{"saveVersion":1,"progress":{},"flags":{"tutorialDone":true}}',
+    });
+    final repo = await SaveRepository.open();
+    expect(repo.adsRemoved, isFalse);
+    expect(repo.tutorialDone, isTrue);
+  });
+}