Show warning when Admin notification has no email addresses configured

After creating a new form, it's easy to overlook configuring Admin notification recipients. The "Admin notification" section in Form Settings → After submit shows "No email addresses added yet" but there is no visual indicator in the form editor or forms list.
As a result, a form can go live and collect submissions without the admin ever receiving notifications — the issue is only discovered when someone notices emails are not arriving.
Suggested improvement: add a warning banner, badge, or indicator in the form editor when Admin notification has no email addresses configured. Similar to the existing warning shown when the email sender field flag is not set.