Refactor i18n setup and improve structure for maintainability

- Relocated `i18n` configuration files to `src/lib/i18n` for better organization.
- Removed obsolete `request.ts` and `routing.ts` files, simplifying `i18n` setup within the project.
- Added extensive tests for `i18n/utils` to validate locale-related utilities, including locale name, native name, and flag retrieval.
- Introduced a detailed `I18N_IMPLEMENTATION_PLAN.md` to document implementation phases, decisions, and recommendations for future extensions.
- Enhanced TypeScript definitions and modularity across i18n utilities for improved developer experience.

frontend/src/lib/i18n/request.ts

@@ -0,0 +1,44 @@
+// src/i18n/request.ts
+/**
+ * Server-side i18n request configuration for next-intl.
+ *
+ * This file handles:
+ * - Loading translation messages for the requested locale
+ * - Server-side locale detection
+ * - Time zone configuration
+ *
+ * Important:
+ * - This runs on the server only (Next.js App Router)
+ * - Translation files are NOT sent to the client (zero bundle overhead)
+ * - Messages are loaded on-demand per request
+ */
+
+import { getRequestConfig } from 'next-intl/server';
+import { routing } from '@/lib/i18n/routing';
+
+export default getRequestConfig(async ({ locale }) => {
+  // Validate that the incoming `locale` parameter is valid
+  // Type assertion: we know locale will be a string from the URL parameter
+  const requestedLocale = locale as 'en' | 'it';
+
+  // Check if the requested locale is supported, otherwise use default
+  const validLocale = routing.locales.includes(requestedLocale)
+    ? requestedLocale
+    : routing.defaultLocale;
+
+  return {
+    // Return the validated locale
+    locale: validLocale,
+
+    // Load messages for the requested locale
+    // Dynamic import ensures only the requested locale is loaded
+    messages: (await import(`../../messages/${validLocale}.json`)).default,
+
+    // Optional: Configure time zone
+    // This will be used for date/time formatting
+    // timeZone: 'Europe/Rome', // Example for Italian users
+
+    // Optional: Configure now (for relative time formatting)
+    // now: new Date(),
+  };
+});

frontend/src/lib/i18n/routing.ts

@@ -0,0 +1,47 @@
+// src/i18n/routing.ts
+/**
+ * Internationalization routing configuration for next-intl.
+ *
+ * This file defines:
+ * - Supported locales (en, it)
+ * - Default locale (en)
+ * - Routing strategy (subdirectory pattern: /[locale]/path)
+ *
+ * Architecture Decision:
+ * - Using subdirectory pattern (/en/about, /it/about) for best SEO
+ * - Only 2 languages (EN, IT) as template showcase
+ * - Users can extend by adding more locales to this configuration
+ */
+
+import { defineRouting } from 'next-intl/routing';
+import { createNavigation } from 'next-intl/navigation';
+
+/**
+ * Routing configuration for next-intl.
+ *
+ * Pattern: /[locale]/[pathname]
+ * Examples:
+ * - /en/about
+ * - /it/about
+ * - /en/auth/login
+ * - /it/auth/login
+ */
+export const routing = defineRouting({
+  // A list of all locales that are supported
+  locales: ['en', 'it'],
+
+  // Used when no locale matches
+  defaultLocale: 'en',
+
+  // Locale prefix strategy
+  // - "always": Always show locale in URL (/en/about, /it/about)
+  // - "as-needed": Only show non-default locales (/about for en, /it/about for it)
+  // We use "always" for clarity and consistency
+  localePrefix: 'always',
+});
+
+// Lightweight wrappers around Next.js' navigation APIs
+// that will consider the routing configuration
+export const { Link, redirect, usePathname, useRouter } = createNavigation(routing);
+
+export type Locale = (typeof routing.locales)[number];

frontend/src/lib/i18n/utils.ts

@@ -2,11 +2,10 @@
 /**
  * Utility functions for internationalization.
  *
- * This file demonstrates type-safe translation usage.
+ * This file provides pure utility functions for i18n without React dependencies.
+ * For React hooks, see hooks.ts
  */
 
-import { useTranslations } from 'next-intl';
-
 /**
  * Get the display name for a locale code.
  *
@@ -54,28 +53,6 @@ export function getLocaleFlag(locale: string): string {
   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.