multicast in source builds from vulnerable setuptools dependency

Summary

### Impact * Some source-builds may be impacted by a CWE-1395 (eg. vulnerable `setuptools` dependency). * Multicast prior to v2.0.9a3 on systems with minimal dependancies installed may use `setuptools <78.1.1` and thus rely on a compromised dependency. In some cases there is a chance that source-builds would fail due to an exploit of the closely related CVE-2025-47273, or become arbitrarily modified. ### Patches * Pre-release version v2.0.9a0 and later resolve the issue by bumping requirements to `setuptools>=80.4` * Pre-release version v2.0.9a3 and later are recommended for improved stability over v2.0.9a0 ### Workarounds * Further hardening in v2.0.9a4+ of the build process in CI builds allowing source builds to be verified via GH attestations. ### References * [GHSA-5rjg-fvgr-3xxf](https://github.com/pypa/setuptools/security/advisories/GHSA-5rjg-fvgr-3xxf) * pypa/setuptools#4946 ### Fixes * https://github.com/reactive-firewall/multicast/blob/c5c7c7de272421d944beca8452871bca6bfd151f/tests/requirements.txt#L32 * https://github.com/reactive-firewall/multicast/blob/c5c7c7de272421d944beca8452871bca6bfd151f/docs/requirements.txt#L27 * https://github.com/reactive-firewall/multicast/blob/c5c7c7de272421d944beca8452871bca6bfd151f/requirements.txt#L26 * https://github.com/reactive-firewall/multicast/blob/c5c7c7de272421d944beca8452871bca6bfd151f/pyproject.toml#L2