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

backend/src/config/db.ts

@@ -0,0 +1,17 @@
+import mysql from 'mysql2/promise';
+import dotenv from 'dotenv';
+
+dotenv.config();
+
+const pool = mysql.createPool({
+    host: process.env.DB_HOST,
+    user: process.env.DB_USER,
+    password: process.env.DB_PASSWORD,
+    database: process.env.DB_NAME,
+    port: Number(process.env.DB_PORT) || 3306,
+    waitForConnections: true,
+    connectionLimit: 10,
+    queueLimit: 0
+});
+
+export default pool;