Notify question authors via Resend when an admin posts the first answer.

Require email at registration (editable on profile), add a Resend mailer with idempotent first-answer sends, and keep answer saves independent of delivery.

.env.example

@@ -14,6 +14,11 @@ SECURE_COOKIE=0
 # Comma-separated CIDRs of reverse proxies allowed to set X-Forwarded-For
 # (direct peer must match). Leave unset to ignore XFF and use RemoteAddr.
 # TRUSTED_PROXY_CIDRS=10.0.0.0/8,192.168.0.0/16
+# Resend (answer notifications). Leave RESEND_API_KEY unset to disable.
+# RESEND_API_KEY=re_xxxxxxxxx
+# RESEND_FROM=Ask a Plumber <notify@yourdomain.com>
+# Public site origin used in email links (required when Resend is enabled):
+# APP_BASE_URL=https://askaplumber.example
 # DigitalOcean Spaces (profile avatars). Leave unset to disable uploads.
 # SPACES_KEY=
 # SPACES_SECRET=