- Added `dispatcharr.settings_test` for isolated testing, automatically creating an empty PostgreSQL test database and ensuring transaction isolation during tests.
- Updated `manage.py` to switch to the test settings when running tests.
- Enhanced the CONTRIBUTING.md file with detailed instructions on running the backend test suite and handling Celery tasks in tests.
- Refactored test cases to use static methods for `worker_id` in `test_process_label.py` and adjusted assertions in `test_user_preferences.py` for better clarity and correctness.
