NIP-46 logout method: a connected app can now end its own session. On receiving a logout request the daemon revokes the corresponding KeyUser (via the standard revoke path: ACL cache invalidation, per-app subscription cleanup, and the live app:revoked SSE event) and replies "ack". It is self-scoped (the target is always the requesting client-pubkey, never taken from params) so it needs no approval, and idempotent (acks even when there is no active session). Implements the NIP-46 logout proposal; per the spec it is advisory, so it complements rather than replaces admin revoke/suspend.
Logout shows in the activity feed: because a logout arrives from the app over a relay (rather than being performed by the operator in the UI), it is recorded as an auto-approved action so the session end is visible and auditable instead of the app silently vanishing from the connected list. The request details view describes the logout operation explicitly.
