outboxFlushIntervalMillis

Target cadence for the periodic background outbox flush, in milliseconds. Defaults to 900 000 ms (15 minutes).

Platform behavior: on Android this sets the WorkManager periodic interval; WorkManager enforces a 15-minute minimum, so smaller values are clamped (both here and by the OS). On iOS it is a lower-bound hint for BGTaskScheduler, which still schedules opportunistically.