feat: add CalDAV settings UI and team management pages (Phase 3P)

Backend: PUT /api/tenants/{id}/settings endpoint for updating tenant
settings (JSONB merge). Frontend: /einstellungen page with CalDAV
config (URL, credentials, calendar path, sync toggle, interval),
manual sync button, live sync status display. /einstellungen/team
page with member list, invite-by-email, role management.

frontend/src/app/(app)/einstellungen/team/page.tsx

@@ -0,0 +1,40 @@
+"use client";
+
+import Link from "next/link";
+import { ArrowLeft, Users } from "lucide-react";
+import { TeamSettings } from "@/components/settings/TeamSettings";
+
+export default function TeamPage() {
+  return (
+    <div className="mx-auto max-w-3xl space-y-6 p-4 sm:p-6">
+      <div className="flex items-center gap-3">
+        <Link
+          href="/einstellungen"
+          className="rounded-md p-1.5 text-neutral-400 hover:bg-neutral-100 hover:text-neutral-600"
+        >
+          <ArrowLeft className="h-4 w-4" />
+        </Link>
+        <div className="flex items-center gap-2.5">
+          <Users className="h-4 w-4 text-neutral-500" />
+          <h1 className="text-lg font-semibold text-neutral-900">
+            Team verwalten
+          </h1>
+        </div>
+      </div>
+
+      <section className="rounded-xl border border-neutral-200 bg-white p-5">
+        <div className="border-b border-neutral-100 pb-3">
+          <h2 className="text-sm font-semibold text-neutral-900">
+            Mitglieder
+          </h2>
+          <p className="mt-0.5 text-xs text-neutral-500">
+            Benutzer einladen und Rollen verwalten
+          </p>
+        </div>
+        <div className="mt-4">
+          <TeamSettings />
+        </div>
+      </section>
+    </div>
+  );
+}