Batch scrape many URLs asynchronously with Firecrawl and poll for completion (POST /v2/batch/scrape)

Documented steps

1. AUTH: Authorization: Bearer fc-YOUR_API_KEY; base URL https://api.firecrawl.dev/v2
2. Start: POST https://api.firecrawl.dev/v2/batch/scrape with body {"urls":["https://firecrawl.dev","https://docs.firecrawl.dev"],"formats":["markdown"]}
3. The call returns immediately with {"success":true,"id":"<job-id>","url":"https://api.firecrawl.dev/v2/batch/scrape/<job-id>"} — results are NOT in this response
4. Poll: GET https://api.firecrawl.dev/v2/batch/scrape/{id} with the same Bearer header
5. Check 'status' (scraping | completed | failed) plus 'completed'/'total' counts and 'creditsUsed'
6. When completed, read the 'data' array — one entry per URL with the requested formats and metadata
7. Instead of polling, pass a 'webhook' object in the start request for push notifications (job started / page scraped / completed)
8. Optional start params: maxConcurrency, ignoreInvalidURLs (default true), zeroDataRetention (default false), plus per-page scrape options