Settings > Timers offered a "Default duration", but nothing that creates
a timer ever read it: the keypad starts empty. The row, its preference,
ClockDefaults.timerDuration and the backup field are gone, and the
screen's hint and the hub's subtitle now only speak of the sound.
Backups no longer write default_timer_duration_millis. Older files that
carry it still import, since the codec ignores unknown keys.
Closes#5
clockula-backup-v1.json, schema documented in docs/BACKUP.md per
PLAN.md §7: alarms, timers and world clocks as configuration only —
ring state and a timer's running anchors never leave the device, since
neither means anything on another one. Unknown fields are ignored at
any level; a malformed known field rejects the whole file rather than
importing it half-way.
Import is whole-state replacement, not a merge, and the backup screen
says so before the user confirms. Before replacing: a ringing alarm is
dismissed and every running timer is deleted, so the import can never
strand a live ring session; after it, AlarmEngine and TimerEngine are
told to re-resolve so the imported state is live immediately.
BackupDao adds delete-all/insert-many queries under one transaction —
no schema or version change, queries only.
makiolaj