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/src/components/auth/RegisterForm.tsx

@@ -33,11 +33,7 @@ const createRegisterSchema = (t: (key: string) => string) =>
         .min(1, t('firstNameRequired'))
         .min(2, t('firstNameMinLength'))
         .max(50, t('firstNameMaxLength')),
-      last_name: z
+      last_name: z.string().max(50, t('lastNameMaxLength')).optional().or(z.literal('')), // Allow empty string
-        .string()
-        .max(50, t('lastNameMaxLength'))
-        .optional()
-        .or(z.literal('')), // Allow empty string
       password: z
         .string()
         .min(1, t('passwordRequired'))

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());