fix(validators): add Polish characters support for first/last name validation

- Add ąćęłńóśźżĄĆĘŁŃÓŚŹŻ to regex pattern
- Fixes registration rejecting Polish characters in names

backend/src/middleware/validators.js

@@ -60,14 +60,14 @@ const registerValidation = [
     .trim()
     .isLength({ max: 100 })
     .withMessage('First name must be less than 100 characters')
-    .matches(/^[a-zA-ZÀ-ÿ\s'-]+$/)
+    .matches(/^[a-zA-ZÀ-ÿąćęłńóśźżĄĆĘŁŃÓŚŹŻ\s'-]+$/)
     .withMessage('First name contains invalid characters'),
   body('lastName')
     .optional()
     .trim()
     .isLength({ max: 100 })
     .withMessage('Last name must be less than 100 characters')
-    .matches(/^[a-zA-ZÀ-ÿ\s'-]+$/)
+    .matches(/^[a-zA-ZÀ-ÿąćęłńóśźżĄĆĘŁŃÓŚŹŻ\s'-]+$/)
     .withMessage('Last name contains invalid characters'),
   body('wsdcId')
     .optional({ nullable: true, checkFalsy: true })