refacto: Adding i18n support with FR and EN as base

frontend/js/i18n.js

@@ -0,0 +1,46 @@
+let currentLang = localStorage.getItem('keta_lang') || (navigator.language.startsWith('en') ? 'en' : 'fr');
+let translations = {};
+
+export async function initI18n(lang = currentLang) {
+  currentLang = lang;
+  localStorage.setItem('keta_lang', lang);
+
+  try {
+    const response = await fetch(`./locales/${lang}.json`);
+    translations = await response.json();
+    translatePageDOM();
+    document.documentElement.lang = lang;
+  } catch (error) {
+    console.error(`Erreur de chargement de la langue ${lang}:`, error);
+  }
+}
+
+export function translatePageDOM() {
+  document.querySelectorAll('[data-i18n]').forEach(el => {
+    const key = el.getAttribute('data-i18n');
+    const text = getNestedTranslation(key);
+    if (text) el.textContent = text;
+  });
+
+  document.querySelectorAll('[data-i18n-placeholder]').forEach(el => {
+    const key = el.getAttribute('data-i18n-placeholder');
+    const text = getNestedTranslation(key);
+    if (text) el.placeholder = text;
+  });
+}
+
+export function t(key, params = {}) {
+  let val = getNestedTranslation(key) || key;
+  Object.keys(params).forEach(p => {
+    val = val.replace(`{${p}}`, params[p]);
+  });
+  return val;
+}
+
+function getNestedTranslation(key) {
+  return key.split('.').reduce((obj, i) => (obj ? obj[i] : null), translations);
+}
+
+export function getCurrentLang() {
+  return currentLang;
+}