Two more issues found deploying the previous two commits live:
1. The nodogsplash package's own uci-defaults populate an anonymous
@nodogsplash[0] section pointed at br-lan (see install_and_stop's
doc comment). NoDogSplash runs one gateway instance per config
section, so this ran alongside our own nodogsplash.main instead of
being superseded by it — silently re-gating br-lan. configure() now
deletes it.
2. After `network restart` + `wifi down/up`, netifd intermittently
loses the race to claim br-tollgate as the wifi vif attaches
(reports up:false, DEVICE_CLAIM_FAILED) even though the bridge
device and member interface both exist correctly. NoDogSplash
refuses to start against an interface netifd hasn't brought up.
restart_services() now explicitly cycles just the tollgate
interface (ifdown/ifup) after the wifi restart.