fix: move DevToolbar dynamic import to Client Component

ssr: false is not allowed with next/dynamic in Server Components.
Extracted the dynamic() call into DevToolbarLoader.tsx ('use client')
so layout.tsx stays a pure Server Component.

components/DevToolbarLoader.tsx

@@ -0,0 +1,13 @@
+'use client';
+
+import dynamic from 'next/dynamic';
+
+// ssr: false ist nur in Client Components erlaubt
+const DevToolbar = dynamic(
+  () => import('@/components/DevToolbar').then(m => ({ default: m.DevToolbar })),
+  { ssr: false }
+);
+
+export function DevToolbarLoader() {
+  return <DevToolbar />;
+}