This behavior (which exists on `master` as well) seems like justification for the singleton interface. Even if you instantiate multiple Timers, they're all going to collide when you save them.

If the item name had the alarm ID concatenated to it, maybe we could make timer instances isolated? The application logic would then store an `active_timer_id` separately for use during startup.

Alternatively, I suppose you could provide hooks for saving, and the Timer Panel could define the asyncStorage integration. I know that's just shuffling code around, but it seems confusing to expose `Timer` as a new-able class, but have this internal restriction that essentially forces you to use it as a singleton.