Function supported_currencies 

pub fn supported_currencies(
    security_firm: Option<i32>,
    trd_market: Option<i32>,
    uni_card_num: Option<&str>,
) -> Option<Vec<i32>>

取账户 supported currencies 完整列表 (对齐 C++ INNData_Trd_CommonCurrency::GetAccountValidCurrency line 90-146)

• 期货账户: 按 broker 取 futures set
• 全能账户: 按 broker 取 universal set
• 单币种账户: 仅一个 currency (TrdMarket → Currency 派生)
• broker 未识别: None (无法判断, daemon 不该 hard reject — 让 backend 决定)