When a notification is displayed and rescheduled for the next occurrence,
now also schedule a background fetch to prefetch content 5 minutes before
the next notification time.
- Add DailyNotificationFetcher import to DailyNotificationWorker
- In scheduleNextNotification(), after successfully scheduling notification,
calculate fetch time (5 minutes before next scheduled time)
- Create DailyNotificationFetcher instance and schedule prefetch
- Add logging with DN|RESCHEDULE_PREFETCH_SCHEDULED tag for observability
- Fall back to immediate fetch if fetch time is in the past
This ensures the prefetch → cache → schedule → display pipeline continues
for subsequent notifications, not just the initial scheduling.