- mail
	- MailProvider service registered via DI; SMTP implementation (Mailhog in dev, real SMTP in prod)
	- Jinja2 templates with DE/EN i18n
	- no public routes — used by other apps (e.g. orders) through DI
	- depends on: core
	- room for growth: outbound queue with retries, provider abstraction (SendGrid, Postmark, SES), richer transactional templates, bounce/complaint handling