add missing file

apps/app/next.config.cjs

@@ -0,0 +1,28 @@
+/**
+ * Minimal Next.js config for production runtime.
+ *
+ * next.config.ts is the authoritative config used at build time (Turbopack rules,
+ * transpilePackages, sassOptions, etc.).  However, Next.js 16 tries to transpile
+ * .ts configs at server startup, which fails in production where TypeScript is not
+ * installed.  assemble-prod.sh therefore deletes next.config.ts and renames this
+ * file to next.config.js so the production server can load the runtime-critical
+ * settings (i18n routing, pageExtensions, …) without a TypeScript toolchain.
+ *
+ * Keep the runtime-relevant values in sync with next.config.ts.
+ */
+
+const nextI18nConfig = require('./config/next-i18next.config');
+
+const { i18n } = nextI18nConfig;
+
+/** @type {import('next').NextConfig} */
+module.exports = {
+  reactStrictMode: true,
+  poweredByHeader: false,
+  pageExtensions: ['page.tsx', 'page.ts', 'page.jsx', 'page.js'],
+  i18n,
+
+  serverExternalPackages: [
+    'handsontable',
+  ],
+};