Fetch mit Timeout und Retry

const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

export async function fetchWithRetry(url, { retries = 3, timeout = 5000, backoff = 500, ...opts } = {}) {
  for (let attempt = 0; ; attempt++) {
    try {
      // Eigener Timeout pro Versuch
      const res = await fetch(url, { ...opts, signal: AbortSignal.timeout(timeout) });
      // Nur 429 und 5xx wiederholen, 4xx direkt zurückgeben
      if ((res.status === 429 || res.status >= 500) && attempt < retries) {
        throw new Error(`HTTP ${res.status}`);
      }
      return res;
    } catch (err) {
      if (attempt >= retries) throw err;
      // Exponentieller Backoff mit Jitter
      await sleep(backoff * 2 ** attempt + Math.random() * 100);
    }
  }
}

// in async-Funktion:
// const res = await fetchWithRetry('/api/data', { timeout: 3000, retries: 2 });