Evicting a remote object only deleted its Postgres row. The S3 index and the Redis TTL/ETag keys survived, so stale mirror metadata such as EPEL repodata kept being served.
- evict the artifact row, S3 index and Redis keys via `Engine.Evict`
- evict a directory with `<dir>/*`; other wildcards return 400, unknown remotes 404
- wait on the per-path fetch lock for single-path evicts; return 503 on timeout or a Redis error
- wildcard evicts take no lock; a fetch already in flight may re-cache its path
- return S3 list errors from `DeletePrefix` instead of deleting nothing
Reviewed-on: #128
Co-authored-by: unkin-agent <unkin-agent@unkin.net>
Co-committed-by: unkin-agent <unkin-agent@unkin.net>
