feat(exercice): galerie de 5 images par exercice (ticket #35)

Étend le modèle Drift (tables.dart, app_database.dart/.g.dart), les
entités/use cases/repositories et exercise_library_screen.dart pour
supporter jusqu'à 5 images par exercice au lieu d'une seule. flutter
analyze propre, 63/63 tests verts, build APK debug validé.

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

lib/infrastructure/local/drift_repositories.dart

@@ -14,7 +14,9 @@ final class DriftExerciseRepository implements ExerciseRepository {
     final row = await (database.select(
       database.exercises,
     )..where((table) => table.id.equals(id))).getSingleOrNull();
-    return row == null ? null : _exerciseFromRow(row);
+    return row == null
+        ? null
+        : _exerciseFromRow(row, await _imageMediaIdsForExercise(id));
   }
 
   @override
@@ -26,7 +28,13 @@ final class DriftExerciseRepository implements ExerciseRepository {
               )
               ..orderBy([(table) => OrderingTerm.asc(table.name)]))
             .get();
-    return rows.map(_exerciseFromRow).toList();
+    final exercises = <domain.Exercise>[];
+    for (final row in rows) {
+      exercises.add(
+        _exerciseFromRow(row, await _imageMediaIdsForExercise(row.id)),
+      );
+    }
+    return exercises;
   }
 
   @override
@@ -45,15 +53,31 @@ final class DriftExerciseRepository implements ExerciseRepository {
 
   @override
   Future<void> save(domain.Exercise exercise) async {
-    await _upsertWithChangeLog(
-      database: database,
-      tableName: 'exercises',
-      entityType: 'Exercise',
-      metadata: exercise.metadata,
-      write: () => database
-          .into(database.exercises)
-          .insertOnConflictUpdate(_exerciseCompanion(exercise)),
-    );
+    await database.transaction(() async {
+      await _upsertWithChangeLog(
+        database: database,
+        tableName: 'exercises',
+        entityType: 'Exercise',
+        metadata: exercise.metadata,
+        write: () => database
+            .into(database.exercises)
+            .insertOnConflictUpdate(_exerciseCompanion(exercise)),
+      );
+      await _replaceExerciseImages(database, exercise);
+    });
+  }
+
+  Future<List<String>> _imageMediaIdsForExercise(String exerciseId) async {
+    final rows =
+        await (database.select(database.exerciseImages)
+              ..where(
+                (table) =>
+                    table.exerciseId.equals(exerciseId) &
+                    table.deletedAt.isNull(),
+              )
+              ..orderBy([(table) => OrderingTerm.asc(table.position)]))
+            .get();
+    return rows.map((row) => row.mediaAssetId).toList();
   }
 }
 
@@ -736,6 +760,100 @@ Future<void> _upsertWithChangeLog({
   });
 }
 
+Future<void> _replaceExerciseImages(
+  db.AppDatabase database,
+  domain.Exercise exercise,
+) async {
+  final rows = await (database.select(
+    database.exerciseImages,
+  )..where((table) => table.exerciseId.equals(exercise.metadata.id))).get();
+  final activeRowsByMediaId = {
+    for (final row in rows)
+      if (row.deletedAt == null) row.mediaAssetId: row,
+  };
+  final desiredIds = exercise.imageMediaIds.toSet();
+  final removedRows = activeRowsByMediaId.values
+      .where((row) => !desiredIds.contains(row.mediaAssetId))
+      .toList();
+  await _softDeleteExerciseImageRows(
+    database,
+    removedRows,
+    exercise.metadata.updatedAt,
+  );
+
+  for (var index = 0; index < exercise.imageMediaIds.length; index++) {
+    final mediaId = exercise.imageMediaIds[index];
+    final existing = activeRowsByMediaId[mediaId];
+    final metadata = existing == null
+        ? domain.EntityMetadata(
+            id: _exerciseImageId(exercise.metadata.id, mediaId),
+            createdAt: exercise.metadata.updatedAt,
+            updatedAt: exercise.metadata.updatedAt,
+            originDeviceId: exercise.metadata.originDeviceId,
+          )
+        : _metadataFromRow(existing).touch(exercise.metadata.updatedAt);
+    await _upsertWithChangeLog(
+      database: database,
+      tableName: 'exercise_images',
+      entityType: 'ExerciseImage',
+      metadata: metadata,
+      write: () => database
+          .into(database.exerciseImages)
+          .insertOnConflictUpdate(
+            db.ExerciseImagesCompanion(
+              id: Value(metadata.id),
+              createdAt: Value(metadata.createdAt.toUtc()),
+              updatedAt: Value(metadata.updatedAt.toUtc()),
+              deletedAt: Value(_utcOrNull(metadata.deletedAt)),
+              schemaVersion: Value(metadata.schemaVersion),
+              syncState: Value(_syncStateToDb(metadata.syncState)),
+              localRevision: Value(metadata.localRevision),
+              originDeviceId: Value(metadata.originDeviceId),
+              futureOwnerProfileId: Value(metadata.futureOwnerProfileId),
+              lastSyncedAt: Value(_utcOrNull(metadata.lastSyncedAt)),
+              remoteRevision: Value(metadata.remoteRevision),
+              exerciseId: Value(exercise.metadata.id),
+              mediaAssetId: Value(mediaId),
+              position: Value(index),
+            ),
+          ),
+    );
+  }
+}
+
+Future<void> _softDeleteExerciseImageRows(
+  db.AppDatabase database,
+  List<db.ExerciseImage> rows,
+  DateTime deletedAt,
+) async {
+  for (final row in rows) {
+    final revision = row.localRevision + 1;
+    await (database.update(
+      database.exerciseImages,
+    )..where((table) => table.id.equals(row.id))).write(
+      db.ExerciseImagesCompanion(
+        deletedAt: Value(deletedAt.toUtc()),
+        updatedAt: Value(deletedAt.toUtc()),
+        localRevision: Value(revision),
+        syncState: const Value('deleted'),
+      ),
+    );
+    await _writeChangeLog(
+      database: database,
+      entityType: 'ExerciseImage',
+      entityId: row.id,
+      operation: 'softDelete',
+      localRevision: revision,
+      originDeviceId: row.originDeviceId,
+      createdAt: deletedAt,
+    );
+  }
+}
+
+String _exerciseImageId(String exerciseId, String mediaId) {
+  return 'exercise-image:$exerciseId:$mediaId';
+}
+
 Future<String> _operationForMutation({
   required db.AppDatabase database,
   required String tableName,
@@ -958,7 +1076,6 @@ db.ExercisesCompanion _exerciseCompanion(domain.Exercise exercise) {
     remoteRevision: values[10] as Value<String?>,
     name: Value(exercise.name),
     description: Value(exercise.description),
-    imageMediaId: Value(exercise.imageMediaId),
     videoMediaId: Value(exercise.videoMediaId),
     hasTimeMeasure: Value(exercise.hasTimeMeasure),
     hasRepsMeasure: Value(exercise.hasRepsMeasure),
@@ -974,12 +1091,12 @@ db.ExercisesCompanion _exerciseCompanion(domain.Exercise exercise) {
   );
 }
 
-domain.Exercise _exerciseFromRow(db.Exercise row) {
+domain.Exercise _exerciseFromRow(db.Exercise row, List<String> imageMediaIds) {
   return domain.Exercise(
     metadata: _metadataFromRow(row),
     name: row.name,
     description: row.description,
-    imageMediaId: row.imageMediaId,
+    imageMediaIds: imageMediaIds,
     videoMediaId: row.videoMediaId,
     hasTimeMeasure: row.hasTimeMeasure,
     hasRepsMeasure: row.hasRepsMeasure,