domainaware/parsedmarc 10.4.2 on GitHub

Bumped the mailsuite floor to >=2.3.0, which raises the transitive mail-parser floor to >=4.6.2 and the transitive cryptography floor to >=50.0.0.
Releases and docs deployment are now automated by a tag-triggered GitHub Actions workflow: CI-gated build, PyPI publishing via Trusted Publishing, a GitHub Release with attached distributions, a Docker image push to ghcr.io, and a GitHub Pages docs deploy. The manual build.sh and publish-docs.sh scripts are removed.