Wire season flow: map screen, progress save, win recording, next stage

SaveRepository (versioned JSON over prefs) with best-result merging and
unlock walking; ContentRepository loads the bundled pack; SeasonFlow/
Progress notifiers orchestrate stage start -> win record -> advance.
Season map grid with stars/locks, Home -> Map -> Game navigation,
close button, next-stage action on the win overlay.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/state/progress_notifier.dart

@@ -0,0 +1,28 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../data/save_repository.dart';
+import 'providers.dart';
+
+/// Exposes saved progress as immutable state so screens rebuild when stars
+/// land; persistence goes through [SaveRepository].
+class ProgressNotifier extends Notifier<Map<String, StageProgress>> {
+  @override
+  Map<String, StageProgress> build() =>
+      ref.read(saveRepositoryProvider).snapshot();
+
+  Future<void> record({
+    required String seasonId,
+    required String stageId,
+    required int stars,
+    required int score,
+  }) async {
+    final repo = ref.read(saveRepositoryProvider);
+    await repo.recordResult(
+      seasonId: seasonId,
+      stageId: stageId,
+      stars: stars,
+      score: score,
+    );
+    state = repo.snapshot();
+  }
+}