Sign a Message

POST /sign

Body

{
  "address": "string",
  "userId": "uuid",
  "message": "Hello, World!",
  "network": "Solana" | "Ethereum",
  "requestId": "req-123456"
}

Success

{ "id": "encoded-user-id", "signature": "base64-or-chain-encoded" }

Errors: 400 invalid user/address/wallet; 401 invalid session; 500 signing failed.