Add a config-driven crawl meter (1 USD / 1000 successes by default, retunable
via WEB_CRAWL_MICROS_PER_SUCCESS) mirroring EtlCreditService:
- WebCrawlCreditService (gate -> pre-check -> post-charge) on the unified wallet
- webcrawler indexer: pre-flight credit block + post-charge of the workspace
owner per success, with a web_crawl TokenUsage audit row
- chat scrape_webpage (main + research): fold each successful scrape into the
active turn's token accumulator so it settles with the chat turn
- WEB_CRAWL_CREDIT_BILLING_ENABLED / WEB_CRAWL_MICROS_PER_SUCCESS config + env
- unit tests (service) + integration tests (indexer wiring)
- scripts/e2e_phase3_crawl_billing.py: manual functional e2e (3a/3b/3c)
Co-authored-by: Cursor <cursoragent@cursor.com>
