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>

test/application/media_use_cases_test.dart

@@ -180,6 +180,9 @@ final class _FakeExerciseRepository implements ExerciseRepository {
     return exercise == null ? const [] : [exercise!];
   }
 
+  @override
+  Future<bool> isReferencedByProgram(String id) async => false;
+
   @override
   Future<void> save(Exercise exercise) async {
     saved.add(exercise);

test/presentation/exercise_library_screen_test.dart

@@ -0,0 +1,188 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:gametime/application/application.dart';
+import 'package:gametime/domain/domain.dart';
+import 'package:gametime/presentation/presentation.dart';
+
+void main() {
+  testWidgets('la validation au moins une mesure active bloque la sauvegarde', (
+    tester,
+  ) async {
+    final exerciseRepository = _FakeExerciseRepository();
+    final exerciseUseCases = _exerciseUseCases(exerciseRepository);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: ExerciseFormScreen(
+          exerciseUseCases: exerciseUseCases,
+          mediaUseCases: _mediaUseCases(exerciseRepository),
+        ),
+      ),
+    );
+
+    await tester.enterText(find.byType(TextFormField).first, 'Gainage');
+    await tester.tap(find.widgetWithText(SwitchListTile, 'Temps'));
+    await tester.pump();
+    await tester.dragUntilVisible(
+      find.text('Enregistrer'),
+      find.byType(ListView),
+      const Offset(0, -200),
+    );
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('Enregistrer'));
+    await tester.pump();
+
+    expect(
+      find.text('Active au moins une mesure pour enregistrer.'),
+      findsOneWidget,
+    );
+    expect(exerciseRepository.saved, isEmpty);
+  });
+
+  testWidgets('la liste affiche les badges des mesures disponibles', (
+    tester,
+  ) async {
+    final exercise = Exercise(
+      metadata: _metadata('exercise-1'),
+      name: 'Squat',
+      description: 'Jambes · charge libre',
+      hasTimeMeasure: true,
+      hasRepsMeasure: true,
+      hasScoreMeasure: true,
+      scoreLabel: 'Charge',
+      scoreUnit: 'kg',
+    );
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(body: ExerciseListTile(exercise: exercise)),
+      ),
+    );
+
+    expect(find.text('Squat'), findsOneWidget);
+    expect(find.text('Jambes · charge libre'), findsOneWidget);
+    expect(find.text('Temps'), findsOneWidget);
+    expect(find.text('Répétitions'), findsOneWidget);
+    expect(find.text('Score (kg)'), findsOneWidget);
+  });
+}
+
+ExerciseUseCases _exerciseUseCases(_FakeExerciseRepository repository) {
+  return ExerciseUseCases(
+    repository: repository,
+    clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
+    ids: _FakeIds(),
+    originDeviceId: 'device-1',
+  );
+}
+
+MediaUseCases _mediaUseCases(_FakeExerciseRepository exerciseRepository) {
+  return MediaUseCases(
+    mediaRepository: _FakeMediaAssetRepository(),
+    exerciseRepository: exerciseRepository,
+    storage: _FakeMediaStorage(),
+    clock: _FakeClock(DateTime.utc(2026, 7, 17, 12)),
+    ids: _FakeIds(),
+    originDeviceId: 'device-1',
+  );
+}
+
+EntityMetadata _metadata(String id) {
+  return EntityMetadata(
+    id: id,
+    createdAt: DateTime.utc(2026, 7, 17),
+    updatedAt: DateTime.utc(2026, 7, 17),
+    originDeviceId: 'device-1',
+  );
+}
+
+final class _FakeClock implements Clock {
+  const _FakeClock(this.value);
+
+  final DateTime value;
+
+  @override
+  DateTime now() => value;
+}
+
+final class _FakeIds implements IdGenerator {
+  var _next = 0;
+
+  @override
+  String newId() {
+    _next += 1;
+    return 'id-$_next';
+  }
+}
+
+final class _FakeExerciseRepository implements ExerciseRepository {
+  final exercises = <Exercise>[];
+  final saved = <Exercise>[];
+  var referenced = false;
+
+  @override
+  Future<Exercise?> findById(String id) async {
+    for (final exercise in exercises) {
+      if (exercise.metadata.id == id) {
+        return exercise;
+      }
+    }
+    return null;
+  }
+
+  @override
+  Future<bool> isReferencedByProgram(String id) async => referenced;
+
+  @override
+  Future<List<Exercise>> listActive() async => exercises;
+
+  @override
+  Future<void> save(Exercise exercise) async {
+    saved.add(exercise);
+    exercises.removeWhere((item) => item.metadata.id == exercise.metadata.id);
+    exercises.add(exercise);
+  }
+}
+
+final class _FakeMediaAssetRepository implements MediaAssetRepository {
+  final saved = <MediaAsset>[];
+
+  @override
+  Future<MediaAsset?> findById(String id) async {
+    for (final asset in saved) {
+      if (asset.metadata.id == id) {
+        return asset;
+      }
+    }
+    return null;
+  }
+
+  @override
+  Future<List<MediaAsset>> listActive() async => saved;
+
+  @override
+  Future<void> save(MediaAsset mediaAsset) async {
+    saved.add(mediaAsset);
+  }
+}
+
+final class _FakeMediaStorage implements LocalMediaStorage {
+  @override
+  Future<void> deleteByLocalUri(String localUri) async {}
+
+  @override
+  Future<StoredMediaFile> importFile({
+    required String sourcePath,
+    required MediaKind kind,
+    required String stableFileName,
+  }) async {
+    return StoredMediaFile(
+      localUri: 'file:///tmp/$stableFileName',
+      mimeType: kind == MediaKind.image ? 'image/png' : 'video/mp4',
+      sizeBytes: 1,
+    );
+  }
+
+  @override
+  Future<Set<String>> listManagedLocalUris() async => const {};
+}