Implement extensive localization improvements across forms and components

- Refactored `it.json` translations with added keys for authentication, admin panel, and settings.
- Updated authentication forms (`LoginForm`, `RegisterForm`, `PasswordResetConfirmForm`) to use localized strings via `next-intl`.
- Enhanced password validation schemas with dynamic translations and refined error messages.
- Adjusted `Header` and related components to include localized navigation and status elements.
- Improved placeholder hints, button labels, and inline validation messages for seamless localization.

frontend/tests/__mocks__/next-intl.tsx

@@ -4,7 +4,9 @@
 
 export const useLocale = jest.fn(() => 'en');
 export const useTranslations = jest.fn(() => (key: string) => key);
-export const NextIntlClientProvider = ({ children }: { children: React.ReactNode }) => <>{children}</>;
+export const NextIntlClientProvider = ({ children }: { children: React.ReactNode }) => (
+  <>{children}</>
+);
 export const useFormatter = jest.fn(() => ({}));
 export const useMessages = jest.fn(() => ({}));
 export const useNow = jest.fn(() => new Date());