Add new subscribers to invite digest for coordinators

New paid subscriptions lack a centralized invite queue, leaving community managers to miss invites and onboarding momentum. Add each subscriber to a digest so coordinators can send invites the same day.

Overview

Every paid subscription is a potential community member; when invites get scattered, onboarding momentum stalls. This flow captures subscribers into a curated invite digest so community managers can send welcome invites the same day and speed onboarding.