refactor: simplify trading parameters API and nonce handling

- Change recent_blockhash from required to optional parameter
- Replace separate nonce_account and current_nonce with unified durable_nonce
- Update all examples and documentation to reflect API changes
- Improve nonce cache usage pattern for better developer experience

BREAKING CHANGE: TradeBuyParams and TradeSellParams API has changed
- recent_blockhash is now Option<Hash> instead of Hash
- nonce_account and current_nonce fields replaced with durable_nonce: Option<DurableNonceInfo>

examples/pumpfun_copy_trading/src/main.rs

@@ -128,7 +128,7 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
         mint: mint_pubkey,
         sol_amount: buy_sol_amount,
         slippage_basis_points: slippage_basis_points,
-        recent_blockhash: recent_blockhash,
+        recent_blockhash: Some(recent_blockhash),
         extension_params: Box::new(PumpFunParams::from_trade(&trade_info, None)),
         lookup_table_key: None,
         wait_transaction_confirmed: true,
@@ -136,8 +136,7 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
         close_wsol_ata: false,
         create_mint_ata: true,
         open_seed_optimize: false,
-        nonce_account: None,
-        current_nonce: None,
+        durable_nonce: None,
     };
     client.buy(buy_params).await?;
 
@@ -157,7 +156,7 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
         mint: mint_pubkey,
         token_amount: amount_token,
         slippage_basis_points: slippage_basis_points,
-        recent_blockhash: recent_blockhash,
+        recent_blockhash: Some(recent_blockhash),
         with_tip: false,
         extension_params: Box::new(PumpFunParams::from_trade(&trade_info, Some(true))),
         lookup_table_key: None,
@@ -165,8 +164,7 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
         create_wsol_ata: false,
         close_wsol_ata: false,
         open_seed_optimize: false,
-        nonce_account: None,
-        current_nonce: None,
+        durable_nonce: None,
     };
     client.sell(sell_params).await?;