.env already exists locally with valid creds (the deleted repo-root
.env was an unused duplicate), and no MailDev infra exists for the
e2e mail tests, so the plan shifts to a MailService unit test plus
one manual send instead of touching .env or standing up e2e infra.
Captures the brainstorming outcome for fixing the broken mail dispatch,
removing the mail-only nestjs-i18n setup in favor of hardcoded German
copy, and redesigning the registration/forgot-password email templates.
