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/ui/screens/home_screen.dart

@@ -1,7 +1,7 @@
 import 'package:flutter/material.dart';
 
 import '../../l10n/gen/app_localizations.dart';
-import 'game_screen.dart';
+import 'season_map_screen.dart';
 
 class HomeScreen extends StatelessWidget {
   const HomeScreen({super.key});
@@ -33,7 +33,7 @@ class HomeScreen extends StatelessWidget {
                 onPressed: () {
                   Navigator.of(context).push(
                     MaterialPageRoute(
-                      builder: (_) => const GameScreen(),
+                      builder: (_) => const SeasonMapScreen(),
                     ),
                   );
                 },