Refactor i18n to use ICU and sentences

.gitignore

@@ -27,6 +27,7 @@ next-env.d.ts
 .DS_Store
 *.pem
 .idea
+.opencode
 
 # debug
 npm-debug.log*

next-i18next.config.js

@@ -1,28 +1,22 @@
+// @ts-expect-error i18next-icu's CommonJS export has an invalid ambient module declaration.
+import ICUModule from 'i18next-icu/cjs';
+
+const ICU = ICUModule.default ?? ICUModule;
+
 /** @type {import('next-i18next').UserConfig} */
 const config = {
   i18n: {
-    defaultLocale: 'default',
-    locales: [
-      'default',
-      'en',
-      'de',
-      'fr',
-      'it',
-      'cs',
-      'nl',
-      'pl',
-      'pt-PT',
-      'pt-BR',
-      'sv',
-      'es',
-      'es-MX',
-      'es-AR',
-      'id',
-      'hu',
-    ],
+    defaultLocale: 'en',
+    locales: ['en', 'it'],
     localeDetection: false,
   },
+  defaultNS: 'common_icu',
+  fallbackLng: 'en',
   localePath: './public/locales',
+  onPreInitI18next: (i18n) => {
+    i18n.use(ICU);
+  },
+  serializeConfig: false,
 };
 
 export default config;

package.json

@@ -51,7 +51,9 @@
     "i18next": "^25.10.10",
     "i18next-browser-languagedetector": "^8.2.1",
     "i18next-http-backend": "^3.0.6",
+    "i18next-icu": "^2.4.1",
     "input-otp": "^1.2.3",
+    "intl-messageformat": "^10.7.18",
     "lucide-react": "^0.544.0",
     "nanoid": "^5.0.6",
     "next": "15.5.18",