Ensure custom images are built from custom base image

[cmgrote]

Note

Compute and use a branch-aware build_version in the custom-package container workflow, and pass it as the VERSION build-arg when building images.

• CI / Workflow (.github/workflows/custom-package-container.yml):
  • Tag/Version logic: Add build_version output; for manual runs append sanitized branch to ${{ inputs.version }}, else use ${{ inputs.version }}.
  • Image build: Pass VERSION=${{ steps.tags.outputs.build_version }} to docker/build-push-action (replacing direct inputs.version).

^{Written by Cursor Bugbot for commit 40ca6fe. This will update automatically on new commits. Configure here.}