Register a Railgun wallet (address + view key).
curl -X POST http://localhost:3004/privacy/wallet/init \ -H "x-api-key: $API_KEY" \ -H 'Content-Type: application/json' \ -d '{"railgunAddress":"0zk...","viewKey":"..."}'
curl http://localhost:3004/privacy/balances \ -H "x-api-key: $API_KEY"