Fix TS2614 and TS1205 errors

Corrected import/export of Transaction type and fixed isolatedModules error.

src/App.tsx

@@ -1,3 +1,4 @@
+
 import React, { useEffect } from 'react';
 import { Routes, Route } from 'react-router-dom';
 import { BudgetProvider } from './contexts/budget/BudgetContext';