Add ambassador signups to leaderboard for program ops

Ambassador signups from marketing automation don't reach the leaderboard, leaving coordinators without a roster. The workflow creates entries so coordinators see updates same day.

Overview

When ambassador signups sit only inside marketing events, program coordinators lack a single source of truth and outreach stalls. This flow writes each signup into your shared leaderboard so coordinators see updates same day and can act on outreach and rewards.