Function derive_sec_market 

pub fn derive_sec_market(
    ftapi_sec_market: i32,
    trd_market: i32,
    code: &str,
) -> i32

Derive FTAPI TrdSecMarket from explicit value, account market, and code.

Legacy raw-value facade. New code should prefer derive_trd_sec_market at the boundary, then unwrap to i32 only when writing the FTAPI/backend wire.