fix(ai): accept every app language on the chat and status requests

The Coach chat, the document chat and the fenced chat declared their
locale field as de/en, so a body naming French, Korean, Brazilian
Portuguese or any other shipped language was refused with 422 before
resolveServerLocale, which carries every locale, ever saw it. The same
pair sat on the profile update, so an account could not store any other
language there either, and the stored language is what the cookie-blind
background work (the Coach nudge, notification texts) writes in.

All four now take z.enum(locales), and the published contract for the
metric, insight and biomarker status queries and the profile update
lists every UI locale instead of two.

src/components/insights/coach-panel/use-coach.ts

@@ -1,5 +1,6 @@
 "use client";
 
+import type { Locale } from "@/lib/i18n/config";
 import {
   useCallback,
   useEffect,
@@ -895,7 +896,7 @@ export interface SendCoachMessageParams {
   conversationId?: string;
   message: string;
   prefill?: string;
-  locale?: "en" | "de";
+  locale?: Locale;
   /**
    * v1.4.20.1 — optional snapshot scope (per-source toggles + window)
    * driven by the sources-rail picker. When omitted the server falls