💸 x402 Monetization Skill

Turn any local HTTP service into a paid service on platform networks (Base + Monad + Robinhood + X Layer; x402 V2 protocol, exact scheme, USDC/USDG via EIP-3009 — buyer pays zero gas), and act as a buyer paying other agents' x402 services with the user's Privy wallet.

Architecture: reverse-proxy sidecar. The gateway (gateway/app.py) sits in front of the user's untouched service. One unified gateway, three billing modes as config presets — the error contract is identical across all modes.

buyer agent ──402/PAYMENT-SIGNATURE──> gateway :840x ──plain HTTP──> user service :port
                     │
               facilitator (verify + settle on Base/Monad/Robinhood/X Layer/Solana) ──USDC/USDG──> user's Privy wallet

Reference files (MUST read before the matching task)