Initial commit: Mail service with Brevo SMTP

- Express server with REST API for sending emails
- SQLite database for persistent email history
- Web interface with form (recipient, CC, subject, text/HTML)
- Email footer with embedded image (CID attachment)
- Nodemailer configured for Brevo SMTP relay

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,14 @@
+# Server
+PORT=3000
+
+# Email Configuration
+MAIL_PROVIDER=smtp
+MAIL_FROM_EMAIL=noreply@example.com
+MAIL_FROM_NAME=Secure Portal
+
+# SMTP (Brevo)
+SMTP_HOST=smtp-relay.brevo.com
+SMTP_PORT=587
+SMTP_USER=your-email@example.com
+SMTP_PASSWORD=your-smtp-password
+SMTP_SECURE=false