Configure trusted PyPI publishing

[ravenSanstete]

Summary

• switch PyPI publishing workflow to GitHub Trusted Publishing/OIDC
• exclude local web runtime caches and node_modules from package artifacts
• add repository and issue URLs to package metadata

Verification

• python -m build --outdir /private/tmp/snowl-pypi-check-20260428
• python -m twine check /private/tmp/snowl-pypi-check-20260428/snowl-0.1.0.tar.gz /private/tmp/snowl-pypi-check-20260428/snowl-0.1.0-py3-none-any.whl
• workflow_dispatch Publish to PyPI run 25049077061 succeeded
• PyPI JSON confirms snowl 0.1.0 wheel and sdist are published