Release v1.1.0

ci: add CI and release workflows with SHA256 checksums

CI workflow: runs tests, build, and vet on every push/PR.
Release workflow: on tag push (v*), builds darwin/arm64 and
darwin/amd64 binaries, generates SHA256 checksums, and creates
a GitHub Release with all artifacts attached.

Version is injected at build time via -ldflags.

Usage:
  git tag v1.0.0 && git push --tags

Release artifacts:
  container-compose-darwin-arm64
  checksums.txt