Render all click help through rich-click, themed by a new `theme` config key (9 palettes + aliases, previewable via `unshackle env theme`), and show service docstrings in local and remote `dl <TAG> -h`.
api-only/remote-only serve now authenticates every serve.users key (str-coerced), not just api_secret, so per-user service allowlists apply. RemoteClient tries X-Secret-Key then X-Api-Key on 401 (sticky winner); remote_services.auth_headers prepends extra header names to the defaults.