Function get_ws_public_base_url 

pub fn get_ws_public_base_url(
    product_type: BinanceProductType,
    environment: BinanceEnvironment,
) -> &'static str

Returns the WebSocket public stream base URL for high-frequency book data.

USD-M mainnet uses the dedicated public endpoint for @bookTicker and @depth streams. All other product types and environments fall back to get_ws_base_url.