fix: correct scValToNative result typing

Author: ComputerOracle

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

@@ -82,11 +82,11 @@ export async function simulateContractCall(
       }
     ).prepareTransaction(tx);
 
-    const result = (
-      preparedTx as {
-        result?: { retval: unknown };
-      }
-    ).result?.retval;
+   const result = (
+  preparedTx as {
+    result?: { retval: Parameters<typeof scValToNative>[0] };
+  }
+).result?.retval;
 
     if (result) {
       return scValToNative(result);