fix: redact authorization tokens from trace logs

[EddieHouston]

Summary

• redact the top-level authorization value before logging JSON-RPC requests at TRACE level
• cover both single and newline-delimited batch request paths without changing wire payloads
• preserve unauthenticated trace output byte-for-byte and fail closed if redaction cannot parse a request

Testing

• cargo test --lib --all-features
• cargo clippy --lib --all-features -- -D warnings

Fixes #215

[EddieHouston]

note... had to pin zeroize in new commit due to MSRV: