Clean up duplicate types and achieve full API parity

Remove duplicate type definitions from client.rs, consolidate all types in types.rs as canonical source, add missing BalanceAllowanceParams and AssetType, fix all method signatures to match reference implementation exactly, add all 42 missing API methods for complete compatibility, fix network error constructor calls, remove duplicate get_sampling_markets method. Now have 42 methods matching reference implementation exactly, all data types properly organized and de-duplicated, full drop-in replacement compatibility achieved.

src/lib.rs

@@ -102,6 +102,7 @@ pub use crate::types::{
     ApiKeysResponse, MidpointResponse, PriceResponse, SpreadResponse, TickSizeResponse,
     NegRiskResponse, BookParams, MarketsResponse, SimplifiedMarketsResponse, Market,
     SimplifiedMarket, Token, Rewards, ClientResult, OrderBookSummary, OrderSummary,
+    BalanceAllowanceParams, AssetType,
 };
 
 // Re-export client
@@ -109,7 +110,7 @@ pub use crate::client::{ClobClient, PolyfillClient};
 
 // Re-export compatibility types (for easy migration from polymarket-rs-client)
 pub use crate::client::{
-    OrderArgs, OrderBookSummary,
+    OrderArgs,
 };
 
 // Re-export error types