fix: resolve remaining soroban client type errors

Author: ComputerOracle

frontend/src/lib/contract/soroban-client.ts

@@ -1,4 +1,5 @@
 import { STELLAR_NETWORK, CONTRACT_ID } from "@/lib/env";
+import type { Account, ScVal } from "@stellar/stellar-sdk";
 
 let rpcClient: unknown = null;
 
@@ -41,7 +42,7 @@ export async function simulateContractCall(
     const tempKeypair = Keypair.random();
 
     // Get the account details from RPC
-    const sourceAccount = await (client as { getAccount: (key: string) => Promise<unknown> }).getAccount(tempKeypair.publicKey());
+    const sourceAccount = await (client as { getAccount: (key: string) => Promise<Account> }).getAccount(tempKeypair.publicKey());
 
     // Create contract instance and add operation
     const contract = new Contract(contractId);
@@ -76,7 +77,7 @@ export async function simulateContractCall(
     const preparedTx = await (client as { prepareTransaction: (tx: unknown) => Promise<unknown> }).prepareTransaction(tx);
 
     // Extract result from prepared transaction
-    const result = (preparedTx as { result?: { retval: unknown } }).result?.retval;
+    const result = (preparedTx as { result?: { retval: ScVal } }).result?.retval;
     if (result) {
       return scValToNative(result);
     }