fix(data): race-safe DB open, graceful unknown types, explicit id error + fallback tests

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

test/data/pokemon_repository_test.dart

@@ -49,6 +49,13 @@ class FakeRemote implements PokemonRemoteDataSource {
   }
 }
 
+class ThrowingRemote implements PokemonRemoteDataSource {
+  @override
+  Future<List<Pokemon>> getAll() async => throw Exception('network');
+  @override
+  Future<Pokemon> getById(int id) async => throw Exception('network');
+}
+
 void main() {
   group('getById', () {
     test('retourne le cache local sans appeler l\'API', () async {
@@ -103,4 +110,18 @@ void main() {
       expect(list.length, 3);
     });
   });
+
+  group('repli sur erreur', () {
+    test('getById retourne null si l\'API échoue et le cache est vide', () async {
+      final repo = PokemonRepositoryImpl(remote: ThrowingRemote(), local: FakeLocal());
+      expect(await repo.getById(42), isNull);
+    });
+
+    test('getAll retourne le cache existant si la synchro API échoue', () async {
+      final local = FakeLocal({1: _mk(1)}); // cache incomplet -> tente l'API, qui échoue
+      final repo = PokemonRepositoryImpl(remote: ThrowingRemote(), local: local);
+      final list = await repo.getAll();
+      expect(list.length, 1); // repli sur le cache
+    });
+  });
 }