Add daily streak system and normalize bundle id to com.airkjw.blockseasons

Pure advanceStreak (1-day grace none, milestone flags at 3/7/14/30),
persisted in the save blob; StreakNotifier advances on every finished
attempt; home screen flame chip and milestone snackbar. Fix flutter
create's camelCased iOS bundle id and underscored Android application
id to the agreed lowercase form before any store registration.

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

lib/data/save_repository.dart

@@ -2,6 +2,8 @@ import 'dart:convert';
 
 import 'package:shared_preferences/shared_preferences.dart';
 
+import 'streak.dart';
+
 class StageProgress {
   const StageProgress({required this.stars, required this.bestScore});
 
@@ -24,6 +26,14 @@ class SaveRepository {
           bestScore: value['bestScore'] as int,
         );
       }
+      final streak = json['streak'] as Map<String, dynamic>?;
+      if (streak != null) {
+        _streak = StreakState(
+          current: streak['current'] as int,
+          best: streak['best'] as int,
+          lastYmd: streak['lastYmd'] as String?,
+        );
+      }
     }
   }
 
@@ -34,6 +44,14 @@ class SaveRepository {
 
   final SharedPreferences _prefs;
   final Map<String, StageProgress> _progress = {};
+  StreakState _streak = StreakState.initial;
+
+  StreakState get streak => _streak;
+
+  Future<void> saveStreak(StreakState streak) {
+    _streak = streak;
+    return _flush();
+  }
 
   static String _id(String seasonId, String stageId) => '$seasonId/$stageId';
 
@@ -88,6 +106,11 @@ class SaveRepository {
                 'bestScore': entry.value.bestScore,
               },
           },
+          'streak': {
+            'current': _streak.current,
+            'best': _streak.best,
+            'lastYmd': _streak.lastYmd,
+          },
         }),
       );
 }