Mode 'active' and the advertise toggle could re-enable the SSID-pool
broadcast that segfaults pineapd. active preset now skips ssidpool/enable
(advertise stays false), the advertise endpoint refuses with an
explanation when the pool is disabled, get_ap reports the real pool
state, and the PineAP overview disables the toggle with a notice. Added
a top-bar health chip (PINEAP OK / POOL OFF / PINEAPD DOWN) polled every
15s.