Validate proof claims without leaking gateway responses

[saviro-orin]

Problem

Airnode accepted a proof after comparing only URL and method, even when the returned claim disagreed with requested headers, body, or response matchers. Non-OK gateway response bodies were also copied into errors and logs, where a gateway could echo upstream credentials.

Changes

• compare requested headers, body, and response matchers against returned claim parameters
• omit gateway response bodies from errors
• add regression coverage for mismatched headers and secret-bearing gateway errors
• document that proof gateways receive upstream credentials

Verification

• bun run lint:prettier
• bun run lint:eslint
• bunx tsc --noEmit
• bun run test:unit, 574 passed
• book production build passed