refactor(i18n): optimize translation loading and initialization

- Updated ensureTranslationsLoaded function to prevent duplicate requests by caching loaded translations and managing loading promises.
- Simplified translation preloading on app startup to only load essential namespaces for the current language.
- Adjusted useTranslationPreloader hook to avoid multiple requests for translations and ensure efficient loading state management.

worklenz-frontend/src/App.tsx

@@ -2,7 +2,6 @@
 import React, { Suspense, useEffect, memo, useMemo, useCallback } from 'react';
 import { RouterProvider } from 'react-router-dom';
 import i18next from 'i18next';
-import { ensureTranslationsLoaded } from './i18n';
 
 // Components
 import ThemeWrapper from './features/theme/ThemeWrapper';
@@ -66,8 +65,8 @@ const App: React.FC = memo(() => {
         // Initialize CSRF token
         await initializeCsrfToken();
 
-        // Preload essential translations
-        await ensureTranslationsLoaded();
+        // Note: Translation preloading is handled in i18n.ts initialization
+        // No need to call ensureTranslationsLoaded here to avoid duplicate requests
       } catch (error) {
         if (isMounted) {
           logger.error('Failed to initialize app:', error);