Add email verification for user accounts

Every account created after the first must confirm a 24-hour link
(Lib\Mailer::sendMail(), log-file or MailJet) before AdminAuth::attempt()
allows login, folded into the same generic pass/fail as a disabled account
or wrong password. First user and pre-migration rows are grandfathered;
create-admin-user.php also auto-verifies for lockout recovery.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

App/config.php

@@ -51,4 +51,13 @@ return [
     // `php novaconium/bin/index-content.php` (e.g. from a deploy step):
     // 'content_index_enabled' => true,
     // 'content_index_auto'    => false,
+
+    // Docs: /admin/docs/admin-auth — email verification. Set all four to
+    // switch Lib\Mailer's transactional mail (verification links, not the
+    // contact form) from the zero-dependency log fallback to MailJet:
+    // 'mail_driver'        => 'mailjet',
+    // 'mail_from_email'    => 'noreply@example.com',
+    // 'mail_from_name'     => 'Example Site',
+    // 'mailjet_api_key'    => '...',
+    // 'mailjet_api_secret' => '...',
 ];