build(dockerfile): missing OCI labels (org.opencontainers.image.source, .licenses, .version)

gh issue create --title "build(dockerfile): missing OCI labels (org.opencontainers.image.source, .licenses, .version)" --label "build,audit,priority:low" --body "## Finding

Dockerfile does not set OCI image labels (org.opencontainers.image.source, org.opencontainers.image.licenses, org.opencontainers.image.version, org.opencontainers.image.revision). Container registries use these to render metadata, and `docker inspect` users see them as a contract.

## Affected code

- Dockerfile — LABEL instructions (missing)

## Reproduction

1. `docker inspect | jq '.[0].Config.Labels'`.
2. Observe no OCI labels.

## Suggested fix

Add LABEL statements:

LABEL org.opencontainers.image.source=\"https://github.com/airvzxf/ftp-deployment-action\" \\
org.opencontainers.image.licenses=\"AGPL-3.0\" \\
org.opencontainers.image.version=\"\${VERSION}\"

Pass VERSION via --build-arg. Or use the GitHub Actions `docker/metadata-action` to set them at build time.

## Source

F2 audit 2026-09-03 (Dockerfile/Makefile audit). Reporter: subagent-pekodbj7.

## Related

- Part of EPIC #[epic-number]
- Closes: #NONE (no existing issue)"