Hm, should clients add an nsec field during bunker setup? Not for you to put your real nsec into, but rather one that you know is allowed to post to your relay. Then if the client becomes adversarial the worst they can do is post spam to your relay, which they can probably already do once they have remote signer permissions. This is overbuilt but maybe there is a simpler solution inside. Maybe the bunker URL you paste initially should just include an nsec for the client to use?