Send a test notice to your own address

Renders the real service_notice template through the real provider and sends it to the verified address on your OWN account — nobody else’s. Run this first after wrangler secret put RESEND_API_KEY and EMAIL_ENABLED=true: a wrong EMAIL_FROM, an unverified sending domain or a missing DNS record then shows up here rather than in front of every customer at once. Idempotent to the minute, so a double-click sends one email.