fix: prevent folder scan during NFO processing on startup

- Modified SeriesManagerService to create SerieList with skip_load=True
- Changed scan_and_process_nfo() to load series from database instead of filesystem
- Fixed database transaction issue by creating separate session per task
- Verified scans only run once during initial setup, not on normal startup

tests/unit/test_media_scan_startup.py

@@ -150,7 +150,7 @@ class TestMediaScanStartup:
     async def test_check_incomplete_series_integration(self):
         """Test the _check_incomplete_series_on_startup function behavior."""
         from src.server.database.models import AnimeSeries
-        
+
         # Mock database session
         mock_db = AsyncMock()
         
@@ -185,7 +185,7 @@ class TestMediaScanStartup:
             
             # Import and call the function
             from src.server.fastapi_app import _check_incomplete_series_on_startup
-            
+
             # Mock get_db_session (it's imported inside the function)
             with patch('src.server.database.connection.get_db_session') as mock_get_db:
                 mock_get_db.return_value.__aenter__.return_value = mock_db
@@ -277,7 +277,7 @@ class TestMediaScanStartup:
             mock_get_db.side_effect = Exception("Database connection error")
             
             from src.server.fastapi_app import _check_incomplete_series_on_startup
-            
+
             # Should not raise exception
             try:
                 await _check_incomplete_series_on_startup(mock_background_loader)