What this prototype does and does not prove
All data stays in this page's memory. Playback is visual and clock time is simulated. Permission controls stand in for Android settings; they do not change your computer or phone.
This demo covers timer creation, normal and overnight schedules, start/pause, pattern editing, setup states, and grouped playback. It does not implement Android alarms, actual haptics, background services, reboot recovery, or daylight-saving transitions. Those require the Android implementation and physical-device acceptance.