- Add scripts/ci/acr_cleanup.py for ACR image lifecycle management
- Cleanup strategy: version tags and fixed tags kept forever, PR tags kept 7 days, commit hash tags kept last 20
- Add acr-cleanup job to ci-build.yml, runs after build-staging on main/develop push
- Supports dry-run mode for preview before execution
- Uses Docker Registry V2 API with OCI index support (ACR multi-arch format)