Add internationalization (i18n) with next-intl and Italian translations

- Integrated `next-intl` for server-side and client-side i18n support.
- Added English (`en.json`) and Italian (`it.json`) localization files.
- Configured routing with locale-based subdirectories (`/[locale]/path`) using `next-intl`.
- Introduced type-safe i18n utilities and TypeScript definitions for translation keys.
- Updated middleware to handle locale detection and routing.
- Implemented dynamic translation loading to reduce bundle size.
- Enhanced developer experience with auto-complete and compile-time validation for i18n keys.

frontend/src/lib/i18n/utils.ts

@@ -0,0 +1,109 @@
+// src/lib/i18n/utils.ts
+/**
+ * Utility functions for internationalization.
+ *
+ * This file demonstrates type-safe translation usage.
+ */
+
+import { useTranslations } from 'next-intl';
+
+/**
+ * Get the display name for a locale code.
+ *
+ * @param locale - The locale code ('en' or 'it')
+ * @returns The human-readable locale name
+ */
+export function getLocaleName(locale: string): string {
+  const names: Record<string, string> = {
+    en: 'English',
+    it: 'Italiano',
+  };
+
+  return names[locale] || names.en;
+}
+
+/**
+ * Get the native display name for a locale code.
+ * This shows the language name in its own language.
+ *
+ * @param locale - The locale code ('en' or 'it')
+ * @returns The native language name
+ */
+export function getLocaleNativeName(locale: string): string {
+  const names: Record<string, string> = {
+    en: 'English',
+    it: 'Italiano',
+  };
+
+  return names[locale] || names.en;
+}
+
+/**
+ * Get the flag emoji for a locale.
+ *
+ * @param locale - The locale code ('en' or 'it')
+ * @returns The flag emoji
+ */
+export function getLocaleFlag(locale: string): string {
+  // Map to country flags (note: 'en' uses US flag, could be GB)
+  const flags: Record<string, string> = {
+    en: '🇺🇸', // or '🇬🇧' for British English
+    it: '🇮🇹',
+  };
+
+  return flags[locale] || flags.en;
+}
+
+/**
+ * Hook to get common translations.
+ * This demonstrates type-safe usage of useTranslations.
+ *
+ * @returns Object with commonly used translation functions
+ */
+export function useCommonTranslations() {
+  const t = useTranslations('common');
+
+  return {
+    loading: () => t('loading'),
+    error: () => t('error'),
+    success: () => t('success'),
+    cancel: () => t('cancel'),
+    save: () => t('save'),
+    delete: () => t('delete'),
+    edit: () => t('edit'),
+    close: () => t('close'),
+    confirm: () => t('confirm'),
+  };
+}
+
+/**
+ * Format a relative time string (e.g., "2 hours ago").
+ * This is a placeholder for future implementation with next-intl's date/time formatting.
+ *
+ * @param date - The date to format
+ * @param locale - The locale to use for formatting
+ * @returns Formatted relative time string
+ */
+export function formatRelativeTime(date: Date, locale: string = 'en'): string {
+  const now = new Date();
+  const diffInSeconds = Math.floor((now.getTime() - date.getTime()) / 1000);
+
+  if (diffInSeconds < 60) {
+    return locale === 'it' ? 'proprio ora' : 'just now';
+  } else if (diffInSeconds < 3600) {
+    const minutes = Math.floor(diffInSeconds / 60);
+    return locale === 'it'
+      ? `${minutes} ${minutes === 1 ? 'minuto' : 'minuti'} fa`
+      : `${minutes} ${minutes === 1 ? 'minute' : 'minutes'} ago`;
+  } else if (diffInSeconds < 86400) {
+    const hours = Math.floor(diffInSeconds / 3600);
+    return locale === 'it'
+      ? `${hours} ${hours === 1 ? 'ora' : 'ore'} fa`
+      : `${hours} ${hours === 1 ? 'hour' : 'hours'} ago`;
+  } else {
+    const days = Math.floor(diffInSeconds / 86400);
+    return locale === 'it'
+      ? `${days} ${days === 1 ? 'giorno' : 'giorni'} fa`
+      : `${days} ${days === 1 ? 'day' : 'days'} ago`;
+  }
+}