fix(boosters): address final-review findings

- daily claim: record the claim before granting boosters, so a crash
  mid-claim forfeits at most one reward instead of allowing a re-claim
  (booster farming) on next launch.
- game screen: disarm the booster target synchronously before awaiting,
  so a rapid second board tap can't double-fire a use or stack a dialog.
- new players: seed one of each booster once (idempotent persisted flag),
  fulfilling the spec's starting inventory. Wired in main().

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/data/save_repository.dart

@@ -52,6 +52,9 @@ class SaveRepository {
       _reviewRequested = (json['flags']
               as Map<String, dynamic>?)?['reviewRequested'] as bool? ??
           false;
+      _boostersSeeded = (json['flags']
+              as Map<String, dynamic>?)?['boostersSeeded'] as bool? ??
+          false;
       final boosters = json['boosters'] as Map<String, dynamic>? ?? {};
       for (final t in BoosterType.values) {
         _boosters[t] = boosters[t.name] as int? ?? 0;
@@ -76,6 +79,7 @@ class SaveRepository {
   bool _soundEnabled = true;
   bool _musicEnabled = true;
   bool _reviewRequested = false;
+  bool _boostersSeeded = false;
   final Map<BoosterType, int> _boosters = {
     for (final t in BoosterType.values) t: 0,
   };
@@ -138,6 +142,18 @@ class SaveRepository {
     return true;
   }
 
+  /// Grants one of each booster the first time it ever runs, so a new player
+  /// can try every booster. Idempotent for the app's lifetime via a persisted
+  /// flag — safe to call on every launch.
+  Future<void> seedInitialBoostersIfNeeded() async {
+    if (_boostersSeeded) return;
+    _boostersSeeded = true;
+    for (final t in BoosterType.values) {
+      _boosters[t] = (_boosters[t] ?? 0) + 1;
+    }
+    await _flush();
+  }
+
   String? get dailyLastClaimedYmd => _dailyLastClaimedYmd;
   int get dailyCalendarDay => _dailyCalendarDay;
 
@@ -221,6 +237,7 @@ class SaveRepository {
             'soundEnabled': _soundEnabled,
             'musicEnabled': _musicEnabled,
             'reviewRequested': _reviewRequested,
+            'boostersSeeded': _boostersSeeded,
           },
           'endless': {'best': _endlessBest},
           'boosters': {for (final t in BoosterType.values) t.name: _boosters[t]},