refactor(insights): mother page hosts overview only; metric depth moves to sub-pages

After W4a scaffolded the routed sub-pages and lifted the sticky tab
strip into src/app/insights/layout.tsx, the mother page becomes the
overview-only surface it always wanted to be: Hero + DailyBriefing +
CorrelationRow + TrendsRow + InsightAdvisorCard + CoachDrawer.

What's gone from the page (now lives on the matching sub-page):
  - Six per-section <HealthChart> / <MoodChart> mounts (bp/weight/
    pulse/mood/meds/bmi) with their target-zone + value-band wiring.
  - Per-metric status-card queries (blood-pressure-status,
    weight-status, pulse-status, bmi-status, mood-status,
    medication-compliance-status).
  - All the per-section <InsightStatusCard> + scatter-correlation
    cards (BP × continuity, weight × BP, mood × BP, mood × weight).
  - The bulky helper functions (getBloodPressureSectionStatus,
    getWeightSectionStatus, …, classifyRangeValue) and their imports
    (getBpTargets, buildWeightBandsFromHeight, pulse-targets, etc.).
  - The inline <InsightsSectionNav> mount — superseded by the strip
    that <InsightsLayoutShell> now mounts.

What stays here:
  - HeroStrip (greeting, weekly-report banner, Health Score panel).
  - DailyBriefing (the AI morning paragraph).
  - CorrelationRow (cross-metric hypotheses).
  - TrendsRow (BP / weight / mood mini-charts above each annotation).
  - InsightAdvisorCard (the rich recommendations grid).
  - CoachDrawer — mother-page-only, per Marc's directive.

The two insights-polish guard tests are re-pointed at the new homes
of their assertions: the tab-strip refresh affordance now lives on
the layout shell (src/components/insights/insights-layout-shell.tsx),
and the comparisonBaseline plumbing migrated into the shared
useInsightsLayoutPrefs() hook.

trends-row.test.tsx wraps every render in a QueryClientProvider —
the v1.4.25 W7 timezone change added a useAuth() call inside
<TrendsRow> for chart-side userTimezone plumbing, which needs a
TanStack-Query client at mount time.

src/components/insights/__tests__/trends-row.test.tsx

@@ -1,5 +1,6 @@
 import { describe, it, expect, vi } from "vitest";
 import { renderToStaticMarkup } from "react-dom/server";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import { I18nProvider } from "@/lib/i18n/context";
 
 /**
@@ -10,6 +11,12 @@ import { I18nProvider } from "@/lib/i18n/context";
  * snapshots show the loading skeleton — that's still enough to verify
  * the row's layout chrome (3-up grid wrapper + per-metric annotation
  * slots).
+ *
+ * v1.4.25 W7 added a `useAuth()` call inside `<TrendsRow>` to plumb
+ * `userTimezone` through to the dynamically-imported chart components,
+ * so the test wraps every render in a TanStack-Query provider — the
+ * stub charts never trigger an actual fetch but `useAuth` requires a
+ * client to mount.
  */
 
 vi.mock("next/dynamic", () => ({
@@ -25,8 +32,13 @@ vi.mock("next/dynamic", () => ({
 import { TrendsRow } from "../trends-row";
 
 function render(node: React.ReactNode, locale: "en" | "de" = "en") {
+  const queryClient = new QueryClient({
+    defaultOptions: { queries: { retry: false, staleTime: Infinity } },
+  });
   return renderToStaticMarkup(
-    <I18nProvider initialLocale={locale}>{node}</I18nProvider>,
+    <QueryClientProvider client={queryClient}>
+      <I18nProvider initialLocale={locale}>{node}</I18nProvider>
+    </QueryClientProvider>,
   );
 }