feat: Initialize backend with Express and MySQL, and restructure frontend with new routing and language support.

frontend/vite.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+
+// https://vite.dev/config/
+export default defineConfig({
+  plugins: [react()],
+})