Update sitemaps and improve language handling

- Updated last modification dates in static and tools sitemaps to 2026-04-01.
- Enhanced language switching in the Header component to ensure language resources are loaded before changing the language.
- Added language resource loading logic in i18n configuration to support dynamic loading of language files.
- Improved SEO route page to ensure correct language is set based on URL parameters.
- Adjusted global CSS for deferred sections to optimize rendering.
- Configured Nginx to enable Brotli compression for better performance.

frontend/src/i18n/index.ts

@@ -3,8 +3,57 @@ import { initReactI18next } from 'react-i18next';
 import LanguageDetector from 'i18next-browser-languagedetector';
 
 import en from './en.json';
-import ar from './ar.json';
-import fr from './fr.json';
+
+type SupportedLanguage = 'en' | 'ar' | 'fr';
+
+const loadedLanguages = new Set<SupportedLanguage>(['en']);
+
+const languageLoaders: Record<Exclude<SupportedLanguage, 'en'>, () => Promise<{ default: Record<string, unknown> }>> = {
+  ar: () => import('./ar.json'),
+  fr: () => import('./fr.json'),
+};
+
+function normalizeLanguage(language?: string): SupportedLanguage {
+  const base = (language || '').split('-')[0];
+  return base === 'ar' || base === 'fr' ? base : 'en';
+}
+
+function getInitialLanguage(): SupportedLanguage {
+  if (typeof window === 'undefined') {
+    return 'en';
+  }
+
+  const htmlLanguage = normalizeLanguage(document.documentElement.lang);
+  if (htmlLanguage !== 'en') {
+    return htmlLanguage;
+  }
+
+  try {
+    const stored = localStorage.getItem('i18nextLng');
+    const fromStorage = normalizeLanguage(stored || undefined);
+    if (fromStorage !== 'en') {
+      return fromStorage;
+    }
+  } catch {
+    // no-op
+  }
+
+  return normalizeLanguage(navigator.language);
+}
+
+export async function ensureLanguageResources(language: string) {
+  const normalized = normalizeLanguage(language);
+  if (normalized === 'en' || loadedLanguages.has(normalized)) {
+    return normalized;
+  }
+
+  const module = await languageLoaders[normalized]();
+  i18n.addResourceBundle(normalized, 'translation', module.default, true, true);
+  loadedLanguages.add(normalized);
+  return normalized;
+}
+
+const initialLanguage = getInitialLanguage();
 
 i18n
   .use(LanguageDetector)
@@ -12,11 +61,11 @@ i18n
   .init({
     resources: {
       en: { translation: en },
-      ar: { translation: ar },
-      fr: { translation: fr },
     },
+    lng: initialLanguage,
     fallbackLng: 'en',
     supportedLngs: ['en', 'ar', 'fr'],
+    load: 'languageOnly',
     interpolation: {
       escapeValue: false,
     },
@@ -26,4 +75,12 @@ i18n
     },
   });
 
+if (initialLanguage !== 'en') {
+  void ensureLanguageResources(initialLanguage).then((resolved) => {
+    if (i18n.language !== resolved) {
+      void i18n.changeLanguage(resolved);
+    }
+  });
+}
+
 export default i18n;