FRED series GOLDPMGBD228NLBM and SLVPRUSD do not exist on the free tier.
Replace with Stooq XAU/USD and XAG/USD free CSV endpoint (no API key needed).
Delta = intraday change vs session open. Cache 5 min on Vercel.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>