feat(ui): écran Bibliothèque d'exercices

Ajoute l'écran de bibliothèque d'exercices (presentation/exercise_library_screen.dart)
et ajuste la couche application/domaine (bootstrap, ports, use cases,
entités, repositories Drift) pour l'alimenter. flutter analyze propre,
9/9 tests verts, build APK debug validé.

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

lib/application/app_bootstrap.dart

@@ -1,15 +1,43 @@
-import '../infrastructure/local/app_database.dart';
+import '../infrastructure/local/local.dart';
+import 'application.dart';
 
 final class AppBootstrap {
-  AppBootstrap._({required this.database});
+  AppBootstrap._({
+    required this.database,
+    required this.exerciseUseCases,
+    required this.mediaUseCases,
+  });
 
   final AppDatabase database;
+  final ExerciseUseCases exerciseUseCases;
+  final MediaUseCases mediaUseCases;
 
   static Future<AppBootstrap> create() async {
     final database = AppDatabase.open();
     await database.customSelect('SELECT 1').get();
+    final exerciseRepository = DriftExerciseRepository(database);
+    final mediaRepository = DriftMediaAssetRepository(database);
+    final ids = LocalIdGenerator();
+    const clock = SystemClock();
+    const originDeviceId = 'local-device';
 
-    return AppBootstrap._(database: database);
+    return AppBootstrap._(
+      database: database,
+      exerciseUseCases: ExerciseUseCases(
+        repository: exerciseRepository,
+        clock: clock,
+        ids: ids,
+        originDeviceId: originDeviceId,
+      ),
+      mediaUseCases: MediaUseCases(
+        mediaRepository: mediaRepository,
+        exerciseRepository: exerciseRepository,
+        storage: const PathProviderLocalMediaStorage(),
+        clock: clock,
+        ids: ids,
+        originDeviceId: originDeviceId,
+      ),
+    );
   }
 
   Future<void> dispose() => database.close();