fix: use @pytest_asyncio.fixture for async fixtures in test_engine.py

backend/tests/test_engine.py

@@ -1,4 +1,5 @@
 import pytest
+import pytest_asyncio
 import tempfile
 import os
 from pathlib import Path
@@ -6,7 +7,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from app.models import Source, Job, JobExecution
 from backup.engine import BackupEngine
 
-@pytest.fixture
+@pytest_asyncio.fixture
 async def test_source(db: AsyncSession):
     with tempfile.TemporaryDirectory() as tmpdir:
         # Create test files
@@ -24,7 +25,7 @@ async def test_source(db: AsyncSession):
         await db.refresh(source)
         yield source
 
-@pytest.fixture
+@pytest_asyncio.fixture
 async def test_job(db: AsyncSession, test_source):
     with tempfile.TemporaryDirectory() as tmpdir:
         job = Job(