fix(frontend): read MSW request body once in SettingsDialog test (pristine output)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/shell/SettingsDialog.test.tsx

@@ -65,7 +65,7 @@ test("Salva PUTs the selected settings", async () => {
   server.use(
     http.put("http://localhost:8787/settings", async ({ request }) => {
       body = await request.json();
-      return HttpResponse.json(await request.json());
+      return HttpResponse.json(body);
     }),
   );
   renderDialog();