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/pages/SeoRoutePage.tsx

@@ -1,6 +1,7 @@
 import { useEffect } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useParams } from 'react-router-dom';
+import { ensureLanguageResources } from '@/i18n';
 import { getProgrammaticToolPage, getSeoCollectionPage } from '@/config/seoPages';
 import NotFoundPage from '@/pages/NotFoundPage';
 import SeoCollectionPage from '@/pages/SeoCollectionPage';
@@ -17,9 +18,12 @@ export default function SeoRoutePage() {
   const resolvedLocale = locale === 'ar' ? 'ar' : 'en';
 
   useEffect(() => {
-    if (i18n.language !== resolvedLocale) {
-      void i18n.changeLanguage(resolvedLocale);
-    }
+    if (i18n.language === resolvedLocale) return;
+
+    void (async () => {
+      const resolved = await ensureLanguageResources(resolvedLocale);
+      await i18n.changeLanguage(resolved);
+    })();
   }, [i18n, resolvedLocale]);
 
   if (!slug) {
@@ -35,4 +39,4 @@ export default function SeoRoutePage() {
   }
 
   return <NotFoundPage />;
-}
+}