Let a user pick the Sensiplan double-check's second indicator — cervical
mucus (default) or cervix observation — mirroring the published NFP
standard where the temperature primary sign pairs with one chosen
secondary sign.
- `CycleProfile.secondarySymptom` (MUCUS default | CERVIX) drives which
second sign the engine confirms against. Casual users keep temperature
+ mucus untouched; the choice lives behind the advanced cycle settings.
- `CycleDayLog` gains the three standard cervix signs — position
(LOW/HIGH), firmness (FIRM/SOFT), opening/os (CLOSED/OPEN) — as nullable
columns (migration 0157), wired through Zod, the day-log upsert, the
DTO, the sync feed, backup/restore and OpenAPI. Additive and
back-compatible: existing profiles backfill MUCUS, existing day-logs
keep NULL cervix signs, iOS inherits the fields.
- The engine's `confirmSymptothermal` takes the secondary-symptom choice;
on CERVIX it confirms against `detectCervixPeak` (last fertile-cervix
day followed by three closed days — the cervix-closure rule) instead of
the mucus peak. The double-check still requires BOTH the temperature
shift AND the secondary peak: a single cervix sign never confirms, and
the still-learning gate and conservative posture are unchanged.
Engine derived clean-room from the Arbeitsgruppe-NFP / Raith-Paula &
Frank-Herrmann standard.
