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).

docs/api/openapi.yaml

@@ -6834,6 +6834,8 @@ components:
           type: boolean
         labs:
           type: boolean
+        illness:
+          type: boolean
         achievements:
           type: boolean
         insights:
@@ -12404,6 +12406,9 @@ components:
         labs:
           type: boolean
           description: Whether the "labs" module is enabled for this account.
+        illness:
+          type: boolean
+          description: Whether the "illness" module is enabled for this account.
         achievements:
           type: boolean
           description: Whether the "achievements" module is enabled for this account.
@@ -12424,6 +12429,7 @@ components:
         - workouts
         - recovery
         - labs
+        - illness
         - achievements
         - coach
         - insights