fix: re-enable stale asset pruning

mobile/lib/domain/services/sync_stream.service.dart

@@ -280,8 +280,7 @@ class SyncStreamService {
         return;
       // SyncCompleteV1 is used to signal the completion of the sync process. Cleanup stale assets and signal completion
       case SyncEntityType.syncCompleteV1:
-        return;
-      // return _syncStreamRepository.pruneAssets();
+        return _syncStreamRepository.pruneAssets();
       // Request to reset the client state. Clear everything related to remote entities
       case SyncEntityType.syncResetV1:
         return _syncStreamRepository.reset();

mobile/test/medium/repositories/sync_stream_repository_test.dart

@@ -0,0 +1,64 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/infrastructure/repositories/sync_stream.repository.dart';
+
+import '../repository_context.dart';
+
+void main() {
+  late MediumRepositoryContext ctx;
+  late SyncStreamRepository sut;
+
+  setUp(() {
+    ctx = MediumRepositoryContext();
+    sut = SyncStreamRepository(ctx.db);
+  });
+
+  tearDown(() async {
+    await ctx.dispose();
+  });
+
+  group('pruneAssets', () {
+    test('deletes foreign orphans and keeps owned, partner, and in-album assets', () async {
+      final me = await ctx.newUser();
+      final partner = await ctx.newUser();
+      final stranger = await ctx.newUser();
+      await ctx.newAuthUser(id: me.id);
+      await ctx.newPartner(sharedById: partner.id, sharedWithId: me.id);
+
+      final own = await ctx.newRemoteAsset(ownerId: me.id);
+      final fromPartner = await ctx.newRemoteAsset(ownerId: partner.id);
+      final shared = await ctx.newRemoteAsset(ownerId: stranger.id);
+      await ctx.newRemoteAsset(ownerId: stranger.id);
+
+      final album = await ctx.newRemoteAlbum(ownerId: me.id);
+      await ctx.newRemoteAlbumAsset(albumId: album.id, assetId: shared.id);
+
+      await sut.pruneAssets();
+
+      final remaining = await ctx.db.select(ctx.db.remoteAssetEntity).get();
+      expect(remaining.map((a) => a.id), unorderedEquals([own.id, fromPartner.id, shared.id]));
+    });
+
+    test('does nothing when there is no authenticated user', () async {
+      final stranger = await ctx.newUser();
+      final orphan = await ctx.newRemoteAsset(ownerId: stranger.id);
+
+      await sut.pruneAssets();
+
+      final remaining = await ctx.db.select(ctx.db.remoteAssetEntity).get();
+      expect(remaining.map((a) => a.id), [orphan.id]);
+    });
+
+    test('prunes every stale foreign asset in a large data set', () async {
+      final stranger = await ctx.newUser();
+      await ctx.newAuthUser();
+      for (var i = 0; i < 600; i++) {
+        await ctx.newRemoteAsset(ownerId: stranger.id);
+      }
+
+      await sut.pruneAssets();
+
+      final remaining = await ctx.db.select(ctx.db.remoteAssetEntity).get();
+      expect(remaining, isEmpty);
+    });
+  });
+}

mobile/test/medium/repository_context.dart

@@ -6,6 +6,7 @@ import 'package:immich_mobile/domain/models/asset/base_asset.model.dart';
 import 'package:immich_mobile/domain/models/memory.model.dart';
 import 'package:immich_mobile/domain/models/user.model.dart';
 import 'package:immich_mobile/infrastructure/entities/asset_face.entity.drift.dart';
+import 'package:immich_mobile/infrastructure/entities/auth_user.entity.drift.dart';
 import 'package:immich_mobile/infrastructure/entities/local_album.entity.drift.dart';
 import 'package:immich_mobile/infrastructure/entities/local_album_asset.entity.drift.dart';
 import 'package:immich_mobile/infrastructure/entities/local_asset.entity.drift.dart';
@@ -72,6 +73,20 @@ class MediumRepositoryContext {
         );
   }
 
+  Future<AuthUserEntityData> newAuthUser({String? id, String? email, AvatarColor? avatarColor}) async {
+    id ??= TestUtils.uuid();
+    return await db
+        .into(db.authUserEntity)
+        .insertReturning(
+          AuthUserEntityCompanion(
+            id: .new(id),
+            email: .new(email ?? '$id@test.com'),
+            name: .new('user_$id'),
+            avatarColor: .new(avatarColor ?? TestUtils.randElement(AvatarColor.values)),
+          ),
+        );
+  }
+
   Future<void> newPartner({required String sharedById, required String sharedWithId, bool? inTimeline}) {
     return db
         .into(db.partnerEntity)