feat(reminders): preventive-care surface — wann, was, wo

Add the Vorsorge page and section: an upcoming-reminders list sorted by
server-computed next-due, with a create form (measurement-linked or
free-text, cadence, notify hour, location) and a per-card Erledigt and
delete action. Cards stay neutral-coloured regardless of due state — the
status reads through a discreet badge only, never an alarming tint. Copy
ships in all six locales.

src/app/vorsorge/page.tsx

@@ -0,0 +1,31 @@
+"use client";
+
+import { Loader2 } from "lucide-react";
+
+import { useAuth } from "@/hooks/use-auth";
+import { useMounted } from "@/hooks/use-mounted";
+import { VorsorgeSection } from "@/components/measurement-reminders/vorsorge-section";
+
+/**
+ * v1.17.1 — Vorsorge (preventive-care) reminders page. The dedicated
+ * feature surface for "wann muss ich was wo machen". Auth-gated; the
+ * section component owns the list + create flow.
+ */
+export default function VorsorgePage() {
+  const { isAuthenticated, isLoading } = useAuth();
+  const mounted = useMounted();
+
+  if (!mounted || isLoading) {
+    return (
+      <div className="flex min-h-[40vh] items-center justify-center">
+        <Loader2 className="text-muted-foreground h-6 w-6 animate-spin" />
+      </div>
+    );
+  }
+
+  return (
+    <div className="mx-auto w-full max-w-2xl px-4 py-6">
+      <VorsorgeSection enabled={isAuthenticated} />
+    </div>
+  );
+}