The JsonRpcResponse<T> generic struct already exists in TH-05-ssrf-block.rs
and meets all acceptance criteria:
- Struct exists with jsonrpc, id, result, and error fields
- Derives serde::Deserialize and is generic over T
- All fields are public
- Compiles without errors
Verification: notes/bf-1pky5.md
Closes bf-1pky5
