async function fetchJson(url, timeoutMs = 5000) {
  const controller = new AbortController();
  const timeout = setTimeout(() => controller.abort(), timeoutMs);
  try {
    const response = await fetch(url, { signal: controller.signal });
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    return await response.json();
  } finally {
    clearTimeout(timeout);
  }
}