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/components/admin/Breadcrumbs.tsx

@@ -31,7 +31,7 @@ export function Breadcrumbs() {
     const breadcrumbs: BreadcrumbItem[] = [];
 
     let currentPath = '';
-    segments.forEach((segment) => {
+    segments.forEach((segment: string) => {
       currentPath += `/${segment}`;
       const label = pathLabels[segment] || segment;
       breadcrumbs.push({