Coolify strips .git from the build context, so git CLI calls in
generate:version-info fail during Docker builds. The script now
resolves metadata in priority order: GIT_* env overrides, then
SOURCE_COMMIT (Coolify's injected build arg, shortened to 7 chars),
then git CLI fallback for local builds. Dockerfile passes the ARGs
through as ENV before the build; DEPLOYMENT.md documents the required
'Include Source Commit in Build' setting.
