Move Firebase Template Links to Main Site

## Problem

The links in our Firebase auth emails (e.g. the Email Verification email) currently point to an old version of the site from years ago when it was hosted on Firebase Hosting instead of Vercel. I'm not even sure we know how to deploy to Firebase Hosting anymore, so we should point critical functionality to the real site instead. AFAICT the only functionality that is used are some semi-permanent redirects that direct the user from the link in the email to the Google-provided default Firebase auth endpoints, and we have those redirects in the live version of the site as well.

I'm not sure what level of Firebase access is required to tweak these email templates - something to keep in mind when deciding whether to pick up this task.

## Success Criteria
- [ ] Update the links in the Firebase auth email templates (from the Firebase Console) to use the main MAPLE domain instead of the old Firebase Hosting domain.
- [ ] DEV (`maple-dev.vercel.app`)
- [ ] PROD (`mapletestimony.org`)