First of three phased sub-projects for PeerTube federation. Backend-only:
RemoteKind enum + kind/username config fields (non-breaking), and a blocking
PeerTubeClient (OAuth2, list channels, paginated channel videos, media
resolution, watch URL) mapped into the existing remote types. Headless,
fixture-tested. Editor (phase 2) and browse UI (phase 3) follow.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
