Add a CYCLE_FERTILE_SOON reminder that fires two days before the
predicted fertile-window start. Twice-gated and default-OFF: it only
surfaces when CycleProfile.goal is TRYING_TO_CONCEIVE and fertileWindowStart
is populated, so fertile language never reaches the avoid / general / peri
goals. Reuses the existing cycle-reminder cron, discreet mode, clientManaged
suppression, idempotency ledger, and push-attempts plumbing verbatim; the
body carries the non-medical, not-a-contraceptive framing.