Send onboarding email series to enrolled teaching fellows

Updated fellow records don't start welcome outreach, leaving Teaching Fellows uninformed. The workflow sends staged emails and a calendar link so fellows are ready before the program.

Overview

Manual outreach for incoming Teaching Fellows consumes coordinator time and risks missed pre-program touches. This flow guarantees every enrolled fellow receives the staged welcome messages and a calendar save link within minutes of a record update, so coordinators can focus on program setup and support ahead of training.