Onboarding drop-off reminder
Reminds students who stall during onboarding to come back and finish. A user is considered stalled when they have remained on the same onboarding step for 24 hours or longer without completing it. A first reminder sends at 24h, and a single follow-up sends if they are still stalled 7 days later. If the user completes the step before the reminder sends, the send is suppressed.