feat: Add EIP-712 signing for L1 authentication (src/auth.rs), HMAC-SHA256 for L2 API authentication, create_api_key(), derive_api_key(), create_or_derive_api_key(), Add set_api_creds() for credential management, Add create_order() and create_market_order() with EIP-712 signing, Add post_order() and create_and_post_order() for order submission, Add cancel(), cancel_orders(), cancel_all() for order management, Add OrderBuilder with proper tick size validation and rounding, Add get_orders() with filtering by ID, asset, market, Add get_trades() with filtering by time range, maker, asset, Add OpenOrderParams and TradeParams for query flexibility, Add balance_allowance() for balance and allowance queries, Add notifications() for push notification setup, Add get_midpoints() for efficient multi-token midpoint queries, Add get_prices() for batch bid/ask/mid price retrieval, Add BatchMidpointRequest/Response and BatchPriceRequest/Response types, Replace Decimal with u32 (Price) and i64 (Qty) on hot paths, Add decimal_to_price() and decimal_to_qty() conversion functions

src/decode.rs

@@ -10,7 +10,6 @@ use chrono::{DateTime, Utc};
 use rust_decimal::Decimal;
 use serde::{Deserialize, Deserializer};
 use serde_json::Value;
-use std::collections::HashMap;
 use std::str::FromStr;
 
 /// Fast string to number deserializers