refactor: Update GasFeeStrategy to instance-based API and update docs

examples/nonce_cache/src/main.rs

@@ -106,8 +106,6 @@ async fn create_solana_trade_client() -> AnyResult<SolanaTrade> {
     let swqos_configs: Vec<SwqosConfig> = vec![SwqosConfig::Default(rpc_url.clone())];
     let trade_config = TradeConfig::new(rpc_url, swqos_configs, commitment);
     let solana_trade = SolanaTrade::new(Arc::new(payer), trade_config).await;
-    // set global strategy
-    sol_trade_sdk::common::GasFeeStrategy::set_global_fee_strategy(150000, 500000, 0.001, 0.001);
     println!("✅ SolanaTrade client initialized successfully!");
     Ok(solana_trade)
 }
@@ -126,6 +124,9 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
     let nonce_account_str = Pubkey::from_str("use_your_nonce_account_here")?;
     let durable_nonce = fetch_nonce_info(&client.rpc, nonce_account_str).await;
 
+    let gas_fee_strategy = sol_trade_sdk::common::GasFeeStrategy::new();
+    gas_fee_strategy.set_global_fee_strategy(150000, 500000, 0.001, 0.001);
+
     // Buy tokens
     println!("Buying tokens from PumpFun...");
     let buy_sol_amount = 100_000;
@@ -156,6 +157,7 @@ async fn pumpfun_copy_trade_with_grpc(trade_info: PumpFunTradeEvent) -> AnyResul
         open_seed_optimize: false,
         durable_nonce: durable_nonce,
         fixed_output_token_amount: None,
+        gas_fee_strategy: gas_fee_strategy,
     };
     client.buy(buy_params).await?;