CORE-4588 - add deployment labels to docker image

[monotek]

Type of Change

• Bugfix
• Enhancement / new feature
• Refactoring
• Documentation

Description

Deployment-tracking image labels + configurable metadata namespace

Adds deployment-tracking labels on the built Docker image, mirroring the existing GitOps manifest annotations, and makes both independently toggleable and their key namespace configurable.

What changed

• New deployment-labels input (default true): stamps com.staffbase.deploy.repositoryFullName / commitSha / version onto the built image, using the same values as the annotations.
• New deployment-annotations input (default true): the existing annotation behavior, now opt-out.
• New deployment-domain input (default deploy.staffbase.com): single source of truth for the key namespace — applied verbatim to annotation keys (<domain>/…) and reversed to reverse-DNS for label keys (com.staffbase.deploy.…).

Implementation

• reverse_domain helper in common.sh; dedicated generate-label-prefix.sh + step (keeps generate-tags.sh tag-only).
• Labels gated per-line in the Build step expression; annotations gated in gitops-functions.sh.

Notes

• Labels are baked in at build time, so release/custom retag runs keep the source branch build's labels.
• 95/95 bats tests pass (+7), shellcheck clean.

Docs updated in README.md.

Checklist

• Write tests
• Make sure all tests pass
• Update documentation
• Review the Contributing Guideline and sign CLA
• Reference relevant issue(s) and close them after merging