Function query_crypto_position_account_info 

pub async fn query_crypto_position_account_info(
    backend: &BackendConn,
    acc_id: u64,
    trd_cache: &TrdCache,
    requested_currency: Option<i32>,
) -> Result<()>

Query crypto positions through CMD20631.

C++ 10.7 Trd_GetPositionList.C2S.currency is required for crypto accounts. Forward it as CMD20631 union_currency instead of reusing the non-crypto first-valid fallback.