feat(mental-health): screener UI, locale-aware copy, and OpenAPI surface

Add the opt-in PHQ-9 / GAD-7 questionnaire surface at /insights/mental-wellbeing:
instrument picker, 0–3 item scale, server-scored result with the validated
severity band, the verbatim Pfizer/PHQ attribution, the screening-not-diagnosis
disclaimer, and a calm crisis-resource card on a positive item-9. The surface
deliberately does NOT mount the shared Coach-launch card — mental-health item
content stays out of the AI.

- i18n: full mentalHealth block plus the six new measurement-type labels and the
  longevity-marker catalogue names/descriptions across all six locales
  (de/en/es/fr/it/pl). Instrument item wording uses the validated German text and
  the canonical English elsewhere (re-wording invalidates the score).
- OpenAPI: regenerate the contract for /api/mental-health/assessments (response
  excludes raw item answers by construction).
- Exclude the new manual / instrument types from the HealthKit-counterpart guard.

src/lib/validations/mental-health.ts

@@ -5,7 +5,10 @@
  * it is narrowed from the session in the handler (CLAUDE.md convention).
  */
 import { z } from "zod/v4";
-import { INSTRUMENTS, type InstrumentId } from "@/lib/mental-health/instruments";
+import {
+  INSTRUMENTS,
+  type InstrumentId,
+} from "@/lib/mental-health/instruments";
 
 export const assessmentInstrumentEnum = z.enum(["PHQ9", "GAD7"]);