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/components/i18n/LocaleSwitcher.tsx

@@ -0,0 +1,76 @@
+/**
+ * LocaleSwitcher Component
+ *
+ * Allows users to switch between available locales (EN, IT).
+ * Maintains the current pathname when switching languages.
+ *
+ * Features:
+ * - Dropdown menu with available locales
+ * - Shows current locale with visual indicator
+ * - Preserves pathname when switching
+ * - Accessible with proper ARIA labels
+ * - Translated labels using next-intl
+ */
+
+'use client';
+
+import { useLocale, useTranslations } from 'next-intl';
+import { usePathname, useRouter, type Locale } from '@/lib/i18n/routing';
+import { Button } from '@/components/ui/button';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+import { Check, Languages } from 'lucide-react';
+import { routing } from '@/lib/i18n/routing';
+import { useTransition } from 'react';
+
+export function LocaleSwitcher() {
+  const t = useTranslations('locale');
+  const locale = useLocale();
+  const router = useRouter();
+  const pathname = usePathname();
+  const [isPending, startTransition] = useTransition();
+
+  const handleLocaleChange = (newLocale: Locale) => {
+    startTransition(() => {
+      // Navigate to the same pathname with the new locale
+      router.replace(pathname, { locale: newLocale });
+    });
+  };
+
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <Button
+          variant="ghost"
+          size="sm"
+          className="gap-2"
+          disabled={isPending}
+          aria-label={t('switchLanguage')}
+        >
+          <Languages className="h-4 w-4" aria-hidden="true" />
+          <span className="uppercase text-xs font-semibold">{locale}</span>
+        </Button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        {routing.locales.map((loc) => (
+          <DropdownMenuItem
+            key={loc}
+            onClick={() => handleLocaleChange(loc)}
+            className="cursor-pointer gap-2"
+          >
+            <Check
+              className={`h-4 w-4 ${locale === loc ? 'opacity-100' : 'opacity-0'}`}
+              aria-hidden="true"
+            />
+            <span>{t(loc)}</span>
+            <span className="ml-auto text-xs text-muted-foreground uppercase">{loc}</span>
+          </DropdownMenuItem>
+        ))}
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}