feat: analytics abstraction with debug backend and game event wiring

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

lib/state/providers.dart

@@ -4,6 +4,7 @@ import '../data/content_repository.dart';
 import '../data/save_repository.dart';
 import '../data/streak.dart';
 import '../game/models/season.dart';
+import '../services/analytics_service.dart';
 import '../services/audio_service.dart';
 import 'endless_best_notifier.dart';
 import 'game_session_notifier.dart';
@@ -66,6 +67,10 @@ final endlessBestProvider = NotifierProvider<EndlessBestNotifier, int>(
   EndlessBestNotifier.new,
 );
 
+final analyticsProvider = Provider<AnalyticsService>(
+  (ref) => AnalyticsService(DebugAnalyticsBackend()),
+);
+
 /// The visual theme of whatever season is in play; fallback outside seasons
 /// (home, endless). Pure model — UI converts via ThemeColors.
 final activeThemeProvider = Provider<SeasonTheme>((ref) {