Remove manual semver validation from PR checks. Versions are now
auto-generated on merge to main by counting existing monthly tags.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
The gha cache backend silently fails on Gitea Actions due to Docker
networking issues between the Buildx builder container and the
act_runner cache server. Registry-based caching stores layers on
Docker Hub, which is more reliable for self-hosted runners.