Function to_human_readable_decimal 

pub fn to_human_readable_decimal(_symbol: &str, size: Decimal) -> Decimal

Convert contract units (Decimal) to human-readable size (Decimal).

Arguments

• symbol - The trading symbol (e.g., “BTC-PERP”, “ETH-PERP”)
• size - Size in contract units (Decimal)

Returns

Human-readable size as Decimal (e.g., 1_000_000 -> 1.0 BTC)