Register User

Register the authenticated user's Google OAuth refresh token.

Only browser-session (JWT) callers are accepted. A valid hCaptcha token is required in non-local environments to prevent automated registration.

The user identity (email, full name) is sourced from the immutable Supabase auth identity inside :func:register_user_core. The request body intentionally only carries the OAuth refresh token plus optional profile links — any email/full_name fields a client sends are ignored by the Pydantic schema (ENG-1214).

Args: http_request: The incoming FastAPI request. request: Registration request with the OAuth refresh token. auth: Authenticated user context (JWT-validated).

Returns: UserRegistrationResponse with success status and connection info.