Function get_margin_info 

pub async fn get_margin_info(
    client: &Arc<FutuClient>,
    env: &str,
    acc_id: u64,
    market: &str,
) -> Result<String>

v1.4.95 U2-D: MCP tool futu_get_margin_info — per-account margin info.

与 futu_get_margin_ratio (per-security ratio) 互补: 本 tool 给账户全景.