Refactor i18n integration and update tests for improved localization

- Updated test components (`PasswordResetConfirmForm`, `PasswordChangeForm`) to use i18n keys directly, ensuring accurate validation messages.
- Refined translations in `it.json` to standardize format and content.
- Replaced text-based labels with localized strings in `PasswordResetRequestForm` and `RegisterForm`.
- Introduced `generateLocalizedMetadata` utility and updated layout metadata generation for locale-aware SEO.
- Enhanced e2e tests with locale-prefixed routes and updated assertions for consistency.
- Added comprehensive i18n documentation (`I18N.md`) for usage, architecture, and testing.

frontend/src/app/[locale]/(auth)/login/page.tsx

@@ -1,4 +1,7 @@
+import { Metadata } from 'next';
 import dynamic from 'next/dynamic';
+import { generatePageMetadata, type Locale } from '@/lib/i18n/metadata';
+import { getTranslations } from 'next-intl/server';
 
 // Code-split LoginForm - heavy with react-hook-form + validation
 const LoginForm = dynamic(
@@ -15,6 +18,17 @@ const LoginForm = dynamic(
   }
 );
 
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: 'auth.login' });
+
+  return generatePageMetadata(locale as Locale, t('title'), t('subtitle'), '/login');
+}
+
 export default function LoginPage() {
   return (
     <div className="space-y-6">

frontend/src/app/[locale]/(auth)/password-reset/confirm/page.tsx

@@ -3,9 +3,28 @@
  * Users set a new password using the token from their email
  */
 
+import { Metadata } from 'next';
 import { Suspense } from 'react';
+import { generatePageMetadata, type Locale } from '@/lib/i18n/metadata';
+import { getTranslations } from 'next-intl/server';
 import PasswordResetConfirmContent from './PasswordResetConfirmContent';
 
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: 'auth.passwordResetConfirm' });
+
+  return generatePageMetadata(
+    locale as Locale,
+    t('title'),
+    t('instructions'),
+    '/password-reset/confirm'
+  );
+}
+
 export default function PasswordResetConfirmPage() {
   return (
     <Suspense

frontend/src/app/[locale]/(auth)/password-reset/page.tsx

@@ -3,7 +3,10 @@
  * Users enter their email to receive reset instructions
  */
 
+import { Metadata } from 'next';
 import dynamic from 'next/dynamic';
+import { generatePageMetadata, type Locale } from '@/lib/i18n/metadata';
+import { getTranslations } from 'next-intl/server';
 
 // Code-split PasswordResetRequestForm
 const PasswordResetRequestForm = dynamic(
@@ -22,6 +25,17 @@ const PasswordResetRequestForm = dynamic(
   }
 );
 
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: 'auth.passwordReset' });
+
+  return generatePageMetadata(locale as Locale, t('title'), t('subtitle'), '/password-reset');
+}
+
 export default function PasswordResetPage() {
   return (
     <div className="space-y-6">

frontend/src/app/[locale]/(auth)/register/page.tsx

@@ -1,4 +1,7 @@
+import { Metadata } from 'next';
 import dynamic from 'next/dynamic';
+import { generatePageMetadata, type Locale } from '@/lib/i18n/metadata';
+import { getTranslations } from 'next-intl/server';
 
 // Code-split RegisterForm (313 lines)
 const RegisterForm = dynamic(
@@ -15,6 +18,17 @@ const RegisterForm = dynamic(
   }
 );
 
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: 'auth.register' });
+
+  return generatePageMetadata(locale as Locale, t('title'), t('subtitle'), '/register');
+}
+
 export default function RegisterPage() {
   return (
     <div className="space-y-6">

frontend/src/app/[locale]/forbidden/page.tsx

@@ -3,16 +3,28 @@
  * Displayed when users try to access resources they don't have permission for
  */
 
-/* istanbul ignore next - Next.js type import for metadata */
 import type { Metadata } from 'next';
 import { Link } from '@/lib/i18n/routing';
 import { ShieldAlert } from 'lucide-react';
 import { Button } from '@/components/ui/button';
+import { generatePageMetadata, type Locale } from '@/lib/i18n/metadata';
+import { getTranslations } from 'next-intl/server';
 
-export const metadata: Metadata = /* istanbul ignore next */ {
-  title: '403 - Forbidden',
-  description: 'You do not have permission to access this resource',
-};
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  const t = await getTranslations({ locale, namespace: 'errors' });
+
+  return generatePageMetadata(
+    locale as Locale,
+    t('unauthorized'),
+    t('unauthorizedDescription'),
+    '/forbidden'
+  );
+}
 
 export default function ForbiddenPage() {
   return (

frontend/src/app/[locale]/layout.tsx

@@ -4,6 +4,7 @@ import { notFound } from 'next/navigation';
 import { routing } from '@/lib/i18n/routing';
 import { NextIntlClientProvider } from 'next-intl';
 import { getMessages } from 'next-intl/server';
+import { generateLocalizedMetadata, type Locale } from '@/lib/i18n/metadata';
 import '../globals.css';
 import { Providers } from '../providers';
 import { AuthProvider } from '@/lib/auth/AuthContext';
@@ -23,10 +24,14 @@ const geistMono = Geist_Mono({
   preload: false, // Only preload primary font
 });
 
-export const metadata: Metadata = {
-  title: 'FastNext Template',
-  description: 'FastAPI + Next.js Template',
-};
+export async function generateMetadata({
+  params,
+}: {
+  params: Promise<{ locale: string }>;
+}): Promise<Metadata> {
+  const { locale } = await params;
+  return generateLocalizedMetadata(locale as Locale);
+}
 
 export default async function LocaleLayout({
   children,