fix(insights): point the empty-state CTAs at the existing measurements route

The B4 insights empty-state CTAs (blutdruck, gewicht, puls, bmi)
linked to `/measurements/new`, a route that does not exist; a tap
landed on a Next.js 404. Re-route via `/measurements?add=<TYPE>`,
the parameter the measurements page now consumes. Each CTA picks a
sensible default: BLOOD_PRESSURE for the BP page, WEIGHT for the
weight and BMI pages, PULSE for the pulse page. The mood, sleep,
and medication empty-states already pointed at their own dedicated
routes and need no change.

Add a `?add=<TYPE>` consumer to the measurements page. The consumer
opens the add-measurement dialog with the right `defaultType` on
first render, then `router.replace` strips the param so the back
button returns to a clean `/measurements`. The allow-list mirrors
MEASUREMENT_TYPES inside `measurement-form.tsx` so a stale link
cannot trap the user on an unknown form. The render-driven set-state
pattern follows account-section.tsx and satisfies the
`react-hooks/set-state-in-effect` rule.

src/app/insights/blutdruck/page.tsx

@@ -27,9 +27,12 @@ import { hasMetricData } from "@/lib/insights/metric-availability";
  * assessment, and the chart's target zones tied to the user's age.
  *
  * v1.4.27 F17 — when the user has zero BP observations, the page
- * short-circuits to an empty-state CTA pointing at `/measurements/new`.
- * Apple Health convention: empty surfaces lead to onboarding hints
- * rather than chart skeletons.
+ * short-circuits to an empty-state CTA pointing at
+ * `/measurements?add=BLOOD_PRESSURE`. Apple Health convention: empty
+ * surfaces lead to onboarding hints rather than chart skeletons.
+ * v1.4.27 MB6 — the previous `/measurements/new` href hit a 404; the
+ * measurements page now consumes `?add=<TYPE>` and auto-opens the
+ * dialog with the matching default type.
  */
 interface AnalyticsData {
   summaries: Record<string, DataSummary>;
@@ -79,7 +82,7 @@ export default function InsightsBlutdruckPage() {
           description={t("insights.emptyState.bloodPressure.description")}
           action={
             <Button size="sm" asChild>
-              <Link href="/measurements/new">
+              <Link href="/measurements?add=BLOOD_PRESSURE">
                 {t("insights.emptyState.bloodPressure.cta")}
               </Link>
             </Button>

src/app/insights/bmi/page.tsx

@@ -68,7 +68,9 @@ export default function InsightsBmiPage() {
   // v1.4.27 F17 — BMI is derived from WEIGHT. When no weight readings
   // exist yet, the existing "set your height" branch can never compute
   // anything useful either; surface the empty-state CTA pointing at
-  // `/measurements/new` instead so the user logs the weight first.
+  // `/measurements?add=WEIGHT` instead so the user logs the weight
+  // first. v1.4.27 MB6 — query-param replaces the dead
+  // `/measurements/new` route.
   if (
     isAuthenticated &&
     analytics &&
@@ -86,7 +88,7 @@ export default function InsightsBmiPage() {
           description={t("insights.emptyState.bmi.description")}
           action={
             <Button size="sm" asChild>
-              <Link href="/measurements/new">
+              <Link href="/measurements?add=WEIGHT">
                 {t("insights.emptyState.bmi.cta")}
               </Link>
             </Button>

src/app/insights/gewicht/page.tsx

@@ -76,7 +76,7 @@ export default function InsightsGewichtPage() {
           description={t("insights.emptyState.weight.description")}
           action={
             <Button size="sm" asChild>
-              <Link href="/measurements/new">
+              <Link href="/measurements?add=WEIGHT">
                 {t("insights.emptyState.weight.cta")}
               </Link>
             </Button>

src/app/insights/puls/page.tsx

@@ -71,8 +71,10 @@ export default function InsightsPulsPage() {
 
   // v1.4.27 F17 — gate the sub-page on at least one pulse observation.
   // Brand-new accounts (no manual logs, no Apple-Health upload yet)
-  // see a one-line empty-state with a CTA into `/measurements/new`
-  // rather than a chart skeleton over a blank target band.
+  // see a one-line empty-state with a CTA into
+  // `/measurements?add=PULSE` rather than a chart skeleton over a
+  // blank target band. v1.4.27 MB6 — query-param replaces the dead
+  // `/measurements/new` route.
   if (
     isAuthenticated &&
     analytics &&
@@ -90,7 +92,7 @@ export default function InsightsPulsPage() {
           description={t("insights.emptyState.pulse.description")}
           action={
             <Button size="sm" asChild>
-              <Link href="/measurements/new">
+              <Link href="/measurements?add=PULSE">
                 {t("insights.emptyState.pulse.cta")}
               </Link>
             </Button>

src/app/measurements/page.tsx

@@ -1,22 +1,63 @@
 "use client";
 
-import { useState } from "react";
+import { useEffect, useState } from "react";
 import { useAuth } from "@/hooks/use-auth";
 import { MeasurementForm } from "@/components/measurements/measurement-form";
 import { MeasurementList } from "@/components/measurements/measurement-list";
 import { Button } from "@/components/ui/button";
 import { ResponsiveSheet } from "@/components/ui/responsive-sheet";
 import { Plus, Loader2 } from "lucide-react";
-import { useRouter } from "next/navigation";
-import { useEffect } from "react";
+import { useRouter, useSearchParams } from "next/navigation";
 import { useTranslations } from "@/lib/i18n/context";
 
+// v1.4.27 MB6 — the insights empty-state CTAs link here with a
+// `?add=<TYPE>` query param to auto-open the add-measurement dialog
+// with the right default type. Keep the allow-list aligned with
+// MEASUREMENT_TYPES inside `measurement-form.tsx`; an unknown value
+// is dropped silently so a stale link can never trap the user on a
+// broken form.
+const ALLOWED_ADD_TYPES = new Set([
+  "BLOOD_PRESSURE",
+  "WEIGHT",
+  "PULSE",
+  "BMI",
+  "GLUCOSE",
+  "TEMPERATURE",
+  "BODY_FAT",
+  "HEART_RATE",
+]);
+
 export default function MeasurementsPage() {
   const { isAuthenticated, isLoading } = useAuth();
   const router = useRouter();
-  const [dialogOpen, setDialogOpen] = useState(false);
+  const searchParams = useSearchParams();
   const { t } = useTranslations();
 
+  // v1.4.27 MB6 — read the `?add=<TYPE>` query param during render so
+  // the dialog opens on the first paint (no flash of the page behind
+  // it). The state-from-prop pattern follows `account-section.tsx`:
+  // store the "addToken we acted on" sentinel and let render kick off
+  // the open + replace transition once per param value. The lint rule
+  // `react-hooks/set-state-in-effect` rejects setState from inside an
+  // effect, so the open-on-param work is render-driven instead.
+  const addParam = searchParams.get("add");
+  const [dialogOpen, setDialogOpen] = useState(false);
+  const [defaultType, setDefaultType] = useState<string | undefined>(
+    undefined,
+  );
+  const [consumedAddParam, setConsumedAddParam] = useState<string | null>(null);
+
+  if (addParam && addParam !== consumedAddParam) {
+    setConsumedAddParam(addParam);
+    if (ALLOWED_ADD_TYPES.has(addParam)) {
+      setDefaultType(addParam);
+      setDialogOpen(true);
+    }
+    // Drop the query string so the back-button leaves the user on
+    // `/measurements` rather than re-opening the dialog.
+    router.replace("/measurements");
+  }
+
   useEffect(() => {
     if (!isLoading && !isAuthenticated) {
       router.push("/auth/login");
@@ -50,12 +91,22 @@ export default function MeasurementsPage() {
 
       <ResponsiveSheet
         open={dialogOpen}
-        onOpenChange={setDialogOpen}
+        onOpenChange={(open) => {
+          setDialogOpen(open);
+          if (!open) setDefaultType(undefined);
+        }}
         title={t("measurements.addMeasurement")}
       >
         <MeasurementForm
-          onSuccess={() => setDialogOpen(false)}
-          onCancel={() => setDialogOpen(false)}
+          defaultType={defaultType}
+          onSuccess={() => {
+            setDialogOpen(false);
+            setDefaultType(undefined);
+          }}
+          onCancel={() => {
+            setDialogOpen(false);
+            setDefaultType(undefined);
+          }}
         />
       </ResponsiveSheet>