- Enhanced the pytest workflow in `.gitea/workflows/test.yml` to include `TRAINING_PLANNING_INTEGRATION` for improved testing against the PostgreSQL database.
- Updated `pytest.ini` to clarify integration marker usage, specifying both `ACCESS_LAYER_INTEGRATION` and `TRAINING_PLANNING_INTEGRATION`.
- Revised documentation in `test_training_planning_sections_integration.py` to provide clearer activation instructions for local and CI environments.
- Updated the backend to improve the fetching and insertion of training unit sections, including a new function for handling section items.
- Added documentation notes regarding the unique constraint on `training_unit_sections` and the implications for parallel training streams.
- Updated frontend components and utility functions to reflect changes in the training planning API and to prepare for future enhancements related to parallel streams.
