Log an interaction — call, meeting, email, message, visit, payment, or other — against a contact. The ONE activity-logging door every lane funnels through, so the contact's last_contact_at freshness bumps no matter which surface logged the touch; the bump never moves backward, so importing older history can never regress a fresher touch. Accepts contact_name, contact_email or contact_phone in place of contact_id. NEXT: contact_read to see the bumped last_contact_at.