Add locale switcher component and integrate internationalization improvements

- Introduced `LocaleSwitcher` component for language selection with support for locale-aware dropdown and ARIA accessibility.
- Updated layouts (`Header`, `Breadcrumbs`, `Home`) to include the new locale switcher.
- Expanded localization files (`en.json`, `it.json`) with new keys for language switching.
- Adjusted i18n configuration to enhance routing and message imports.
- Updated Jest module mappings to mock new i18n components and utilities.

frontend/src/lib/i18n/request.ts

@@ -32,7 +32,7 @@ export default getRequestConfig(async ({ locale }) => {
 
     // Load messages for the requested locale
     // Dynamic import ensures only the requested locale is loaded
-    messages: (await import(`../../messages/${validLocale}.json`)).default,
+    messages: (await import(`../../../messages/${validLocale}.json`)).default,
 
     // Optional: Configure time zone
     // This will be used for date/time formatting