feat: Introduce application version display in the frontend footer, showing both frontend and backend versions with integrated build arguments.

frontend/src/App.jsx

@@ -1,12 +1,34 @@
-import React from 'react';
+import React, { useEffect, useState } from 'react';
 import TodoList from './components/TodoList';
+import { getVersion } from './services/api';
 import './App.css';
 
 function App() {
+  const [backendVersion, setBackendVersion] = useState('...');
+  const frontendVersion = import.meta.env.VITE_APP_VERSION || 'dev';
+
+  useEffect(() => {
+    const fetchVersion = async () => {
+      try {
+        const data = await getVersion();
+        setBackendVersion(data.version || 'dev');
+      } catch (error) {
+        console.error('Error fetching backend version:', error);
+        setBackendVersion('unknown');
+      }
+    };
+    fetchVersion();
+  }, []);
+
   return (
-    <main>
-      <TodoList />
-    </main>
+    <div className="app-container">
+      <main className="main-content">
+        <TodoList />
+      </main>
+      <footer className="app-footer">
+        <p>Frontend <code>{frontendVersion}</code> | Backend <code>{backendVersion}</code></p>
+      </footer>
+    </div>
   );
 }