Revoke an OAuth authorization

Revokes the authenticated caller’s authorization for a third-party OAuth app, identified by client_id in the path. This removes the consent and immediately revokes all of that app’s live access and refresh tokens for this user, so the app’s next API call fails and it must request authorization again. Returns a revoked flag and tokens_revoked count, or 404 if the caller has no authorization for that client_id. Scoped strictly to the caller’s own grant; it never affects other users or apps.