feat(domain): fondation domain du score chronométré (ticket #25)

Étend le modèle Drift (tables.dart, app_database.dart/.g.dart), les
entités du domaine, les ports et use cases pour poser les fondations
du score chronométré. build_runner OK, flutter analyze propre, 39/39
tests verts, build APK debug validé.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/presentation/history_screen_test.dart

@@ -287,11 +287,26 @@ final class _FakeActiveSessionRepository implements ActiveSessionRepository {
   @override
   Future<ActiveRestState?> findRestStateById(String id) async => null;
 
+  @override
+  Future<ActiveScoreStopwatchState?> findScoreStopwatchState({
+    required String sessionId,
+    required int programIndex,
+    required int exerciseIndex,
+    required int setIndex,
+  }) async => null;
+
   @override
   Future<List<ActiveRestState>> listRestStates(String sessionId) async {
     return const [];
   }
 
+  @override
+  Future<List<ActiveScoreStopwatchState>> listScoreStopwatchStates(
+    String sessionId,
+  ) async {
+    return const [];
+  }
+
   @override
   Future<List<ActiveSetResult>> listSetResults(String sessionId) async {
     return const [];
@@ -303,6 +318,18 @@ final class _FakeActiveSessionRepository implements ActiveSessionRepository {
   @override
   Future<void> saveRestState(ActiveRestState restState) async {}
 
+  @override
+  Future<void> saveScoreStopwatchState(ActiveScoreStopwatchState state) async {}
+
+  @override
+  Future<void> deleteScoreStopwatchState({
+    required String sessionId,
+    required int programIndex,
+    required int exerciseIndex,
+    required int setIndex,
+    required DateTime deletedAt,
+  }) async {}
+
   @override
   Future<void> saveSetResult(ActiveSetResult result) async {}
 }