In SaaS mode, SAAS_ADMIN_USER must be an email address. It's used as
both the Logto username and primaryEmail. No separate SAAS_ADMIN_EMAIL.
Installer enforces email format in SaaS mode (moved deployment mode
question before admin credentials), accepts any username in standalone.
Sign-in form label changed to "Login".
Removes SAAS_ADMIN_EMAIL from bootstrap, compose template, installers,
and all documentation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
8fe18c7f83