Function spawn_scheduler 

pub fn spawn_scheduler(
    state: Arc<AppState>,
    tick: Duration,
    status: Arc<Mutex<SchedulerStatus>>,
    allow: Arc<HashSet<String>>,
) -> JoinHandle<()> 

Spawn the background refresh loop: every tick, reload the model, refresh any due CALL measures, and save if anything changed. Never panics or exits on a tick error — it logs (eprintln!, matching the CLI daemon’s style) and tries again next tick.