The pyproject.toml release

Added

• A __version__ attribute relying on importlib.metadata.
• A uv.lock lock-file for reproducible builds.

Changed

• Drop official support for Python 3.8.
• Switch from black to ruff for code style.
• Fully migrate to a pyproject.toml-based project.
• Ensure code style consistency (see selected rules in pyproject.toml).
• Extra dependencies are part of the dev dependency group (PEP 735).
• Switch from setuptools to hatchling for building portion.
• Switch from coverage to pytest-cov for test coverage.