estimate gas instead of hardcoded value

examples/hero_vault/agung_send_transaction.rhai

@@ -2,7 +2,7 @@
 // This script demonstrates how to create a wallet from a private key and send tokens
 
 // Define the private key and recipient address
-let private_key = "0x9ecfd58eca522b0e7c109bf945966ee208cd6d593b1dc3378aedfdc60b64f512";
+let private_key = "51c194d20bcd25360a3aa94426b3b60f738007e42f22e1bc97821c65c353e6d2";
 let recipient_address = "0xf400f9c3F7317e19523a5DB698Ce67e7a7E083e2";
 
 print("=== Agung Wallet Transaction Demo ===");

src/hero_vault/ethereum/contract.rs

@@ -114,11 +114,15 @@ pub async fn call_write_function(
     let call_data = function.encode_input(&args)
         .map_err(|e| CryptoError::ContractError(format!("Failed to encode function call: {}", e)))?;
 
+    // Estimate gas
+    let gas = estimate_gas(contract, wallet, provider, function_name, args.clone()).await?;
+    log::info!("Estimated gas: {:?}", gas);
+
     // Create the transaction request with gas limit
     let tx = TransactionRequest::new()
         .to(contract.address)
         .data(call_data)
-        .gas(U256::from(300000)); // Set a reasonable gas limit
+        .gas(gas); // Set a reasonable gas limit
 
     // Send the transaction using the client directly
     log::info!("Sending transaction to contract at {}", contract.address);

src/hero_vault/ethereum/transaction.rs

@@ -1,6 +1,7 @@
 //! Ethereum transaction functionality.
 
 use ethers::prelude::*;
+use ethers::types::transaction::eip2718::TypedTransaction;
 
 use crate::hero_vault::error::CryptoError;
 use super::wallet::EthereumWallet;
@@ -37,7 +38,18 @@ pub async fn send_eth(
         provider.clone(),
         wallet.wallet.clone(),
     );
+    // Estimate gas
+    let tx = TransactionRequest::new()
+        .to(to)
+        .value(amount);
     
+    // Convert TransactionRequest to TypedTransaction explicitly
+    let typed_tx: TypedTransaction = tx.into();
+    let gas = client.estimate_gas(&typed_tx, None)
+        .await
+        .map_err(|e| CryptoError::SerializationError(format!("Failed to estimate gas: {}", e)))?;
+    log::info!("Estimated gas: {:?}", gas);
+
     // Create the transaction
     let tx = TransactionRequest::new()
         .to(to)