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/tests/app/(authenticated)/settings/profile/page.test.tsx

@@ -91,7 +91,7 @@ describe('ProfileSettingsPage', () => {
 
   it('renders without crashing', () => {
     renderWithProvider(<ProfileSettingsPage />);
-    expect(screen.getByText('Profile Settings')).toBeInTheDocument();
+    expect(screen.getAllByText('Profile Settings').length).toBeGreaterThan(0);
   });
 
   it('renders heading', () => {