v0.0.1

Use setuptools_scm for versioning and update CI

Switch package versioning to setuptools_scm (pyproject.toml -> dynamic version) and add setuptools_scm config (guess-next-dev, no-local-version, fallback 0.0.0). Replace hardcoded __version__ in pyneon/__init__.py with importlib.metadata.version lookup and a local fallback to allow source imports. Revamp GitHub Actions workflow to build on pushes to main and v* tags, set fetch-depth: 0 so setuptools_scm can read tags, produce/upload build artifacts, publish dev builds to TestPyPI on main, and publish stable releases to PyPI on v* tags.