Send a lifecycle email two days after a user opts into AI, but only when
the consent was given outside of onboarding (more than three days after
sign-up) so we don't email users who consented during their initial setup.
A daily scheduled command (email:ai-consent-follow-up) selects active
consents accepted two days ago, skips onboarding-era ones, and queues a
drip email. Deduplication reuses the existing UserMailLog drip system, so
no migration is needed. The email is localised via the user's
HasLocalePreference, like the other drip emails.