Canada GST HST rate API + CAD exchange rates

Pay-per-call x402 API (USDC). $0.05 per call on eip155:8453.

• GET /v1/tax — GST/HST/PST/QST rates & calculator
• GET /v1/fx — Bank of Canada CAD exchange rates
• GET /health — free health check

Request Accept: application/json for the machine-readable service descriptor.