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.