gate magic link login on verified email delivery

The login page now only shows the magic link form when a test email has
been sent successfully, not just when an adapter is configured. Saving
email settings or disconnecting clears the flag so the admin must
re-verify after config changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/berrypod_web/live/auth/login.ex

@@ -117,7 +117,7 @@ defmodule BerrypodWeb.Auth.Login do
        form: form,
        trigger_submit: false,
        registration_open: !Accounts.has_admin?(),
-       email_configured: Mailer.email_configured?()
+       email_configured: Mailer.email_verified?()
      )}
   end