Waybar starts before wlsunset (due to ExecStartPre sleep) and only
checks the service status once. ExecStartPost sends SIGRTMIN+11 so
waybar refreshes the nightlight module after wlsunset is ready.
Move nightlight from niri spawn-at-startup to a systemd user service
with After=kanshi.service to ensure all outputs are configured before
wlsunset starts. Toggle now uses enable/disable --now for persistent
state across reboots.