chore: Unify backend express project into ESM (#281)

backend/config/config.js

@@ -1,7 +1,12 @@
-const path = require('path');
+import path from 'path';
+import { fileURLToPath } from 'url';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = path.dirname(__filename);
+
 const databasePath = path.resolve(__dirname, '../database/database.sqlite');
 
-module.exports = {
+export default {
   development: {
     dialect: 'sqlite',
     storage: databasePath,