feat(setup): T05 configure pytest with coverage
- Create pytest.ini with:
- Test discovery configuration (testpaths, python_files)
- Asyncio mode settings
- Coverage configuration (>=90% requirement)
- Custom markers (unit, integration, e2e, slow)
- Update conftest.py with:
- pytest_asyncio plugin
- Shared fixtures (project_root, src_path, temp_dir, mock_env_vars)
- Path configuration for imports
- Add test_pytest_config.py with 12 unit tests
- All tests passing (12/12)
Refs: T05
Completes setup phase T01-T05
28fde3627e