Implement theme switching and enhance dark mode support (#43)

frontend/tailwind.config.js

@@ -0,0 +1,12 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  content: [
+    "./index.html",
+    "./src/**/*.{js,ts,jsx,tsx}",
+  ],
+  darkMode: 'class', // Use class strategy for dark mode
+  theme: {
+    extend: {},
+  },
+  plugins: [],
+}