feat(illness): add the condition-journal MVP behind a born-gated module

Introduce a retrospective illness/condition journal: episodes with a
lifecycle (acute / chronic-ongoing / recurring / flare) and a daily
symptom timeline forked structurally from the cycle log-day surface. The
journal is a record, not a medical device — no prediction or diagnosis UI.

- Register `illness` as a born-gated (opt-in / default-off) module. The
  gate resolver flips the disabled-allowlist default to off for born-gated
  keys, so the surface stays dark until the account opts in from the
  Modules hub. `isIllnessEnabled` + `requireIllnessEnabled` delegate to the
  module foundation (one source of truth) and re-stamp an illness errorCode.
- Episode CRUD under /api/illness: list / create / get / edit / resolve /
  delete, plus a per-episode-day day-log upsert on (episodeId, date). Every
  route wraps apiHandler, Zod-validates with returnAllZodIssues, narrows
  userId from auth, builds data field-by-field, and gates the module.
  Free-text notes encrypt at rest through the shared Bytes codec.
- Log-day sheet (cycle fork): ~8 Jackson/WURSS symptom chips 0-3 + a
  functional-impact group + fever + an encrypted note, one row per day.
- Episode history page + a born-gated nav entry, neutral palette, status
  via a neutral Badge, retrospective-only copy. i18n across all six locales.
- Cover the new routes in the module-route-gate inventory; unit tests for
  the day-log upsert, the gate enforcement, and the born-gated resolver.

The /api/auth/me module map now projects the `illness` flag (openapi.yaml
regenerated).

src/components/layout/nav-model.ts

@@ -10,6 +10,7 @@ import {
   Pill,
   Settings,
   Stethoscope,
+  Thermometer,
   Trophy,
   Waves,
   type LucideIcon,
@@ -97,6 +98,17 @@ export const NAV_DESTINATIONS: ReadonlyArray<NavDestination> = [
     tourId: "nav-labs",
     requiresModule: "labs",
   },
+  // v1.18.1 — the illness/condition journal sits in the clinical spine
+  // next to Labs. Born-gated: `requiresModule: "illness"` reads the
+  // opt-in `illness` key from the resolved module map, so the entry is
+  // absent until the account turns the module on from the Modules hub.
+  {
+    href: "/illness",
+    tKey: "nav.illness",
+    icon: Thermometer,
+    tourId: "nav-illness",
+    requiresModule: "illness",
+  },
   // v1.17.1 — Vorsorge (preventive-care) gets a top-level nav home in the
   // clinical spine, peer to Labs and Recovery. It is a first-class tracking
   // surface ("wann muss ich was wo machen"), not pure configuration, so it