Initial commit: Postfix mail server with SES relay

- Containerized Postfix configuration for mailing list management
- Environment-based configuration for SES credentials
- Template-based config generation for flexibility
- Static virtual aliases (Phase 1)
- Prepared for future web interface and SQL backend (Phase 2+)

Features:
- Docker Compose orchestration
- Secure credential management via .env
- Configurable SMTP host/port
- Git-ignored sensitive files
- Comprehensive documentation

postfix/sasl_passwd.template

@@ -0,0 +1 @@
+[${SMTP_HOST}]:${SMTP_PORT} ${SES_USER}:${SES_PASS}