Every 500 response in the OCI package silently discarded the actual
error, making production debugging impossible. Add slog.Error before
each 500 response with the error and relevant context (repo, digest,
tag, uuid). Add slog.Info for state-mutating successes (manifest push,
blob upload complete, deletions).
Logger is injected into the OCI Handler via constructor, falling back
to slog.Default() if nil.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>