pit-nightly: a nightly pit.world stats email (#39)

Money (summary passes by CoinPay invoice and x402, featured listings),
summaries (page vs snippet, c0mpute models), accounts, newsletter, votes,
directory and CrawlProof traffic, with a 7-day strip. Reads pit.world's
/api/admin/stats.json (PIT_ADMIN_TOKEN from pit-world--prod); Resend and
CrawlProof from fleet-nightly--prod. Counts only.

Co-authored-by: Anthony Ettinger <anthony@profullstack.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

Author: 3 people