All users in SaaS mode must have an email address. The bootstrap creates
the admin user with primaryEmail set to SAAS_ADMIN_EMAIL (defaults to
<SAAS_ADMIN_USER>@<PUBLIC_HOST>). This prevents the admin from being
locked out when self-service registration (which requires email) is
enabled via the Email Connector UI.
Documentation updated across all CLAUDE.md files, .env.example,
user-manual.md, and installer submodule (README, .env.example, compose).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>