Reddit Coin Scraper

Endpoints:
- /scrape (manual trigger)
- /posts?limit=50
- /stats
- /backfill (one-time backfill of new fields)
- /extract?post_id=xyz (test AI extraction)
- /extraction?post_id=xyz (get extraction result)
- /extractions?hash=xxx&limit=100&domain=coins|watches|cameras (HTML table view - requires access hash)
- /test-discord?post_id=xyz (send test notification to sandbox channel)