feat(auth): enable postmark email verification for v0.1.0 launch

- switch email provider from resend (unused) to postmark (creds available)
- re-enable requireEmailVerification now that email path works
- env vars POSTMARK_API_KEY + EMAIL_FROM must be set in Coolify

packages/email/src/providers/index.ts

@@ -1 +1 @@
-export { send } from "./resend";
+export { send } from "./postmark";