Fix prod release tag automation

[moltenbot000]

Summary

• replace date/build-number release tag generation with semver bump inputs
• fetch full history and tags, configure the GitHub Actions bot author, then create and push the annotated release tag before GoReleaser runs
• keep Docker Hub promotion, digest resolution, and provenance attestation behavior while adding release summary output

Validation

• git diff --check
• ./scripts/validate-repo.sh
• env -u MOLTEN_HUB_TOKEN -u MOLTEN_HUB_REGION go test ./...
• go run github.com/rhysd/actionlint/cmd/actionlint@latest .github/workflows/deploy-prod.yml