feat: Add initial frontend dependencies, base CSS, and Gitea Docker build workflow.

frontend/src/App.jsx

@@ -0,0 +1,13 @@
+import React from 'react';
+import TodoList from './components/TodoList';
+import './App.css';
+
+function App() {
+  return (
+    <main>
+      <TodoList />
+    </main>
+  );
+}
+
+export default App;