v29 — kill the surprise 'play artist only' switch on hiccups

Disables librespot's autoplay (radio station fallback when queue exhausts) by default. After a network hiccup desyncs librespot's session state with Spotify's server, the queue appears empty and autoplay was switching the user's playlist over to a radio station based on the current artist without input. Now defaults to stop-at-end-of-queue. Per-device runtime override: set_autoplay kiosk_command with value 'true' or 'false'.