List cyber threat indicators

Lists URLhaus malware URLs, Feodo Tracker C2 servers, and RSS cyber-feed indicators with malware family, tags, and host metadata. Supports x402 pay-per-request. Requests with a valid Bearer token use API-key authentication. Without a Bearer API key, start the x402 flow from the `402 Payment Required` response and `PAYMENT-REQUIRED` header; retry with `PAYMENT-SIGNATURE`.