Add translation for new user role

backend/hu/user.json

@@ -118,6 +118,7 @@
         "auth_code_invalid": "A be\u00edrt k\u00f3d nem \u00e9rv\u00e9nyes",
         "2fa_screen_explica": "A k\u00e9tszint\u0171 hiteles\u00edt\u00e9s enged\u00e9lyez\u00e9s\u00e9hez hozz\u00e1f\u00e9r\u00e9si jogosults\u00e1gra van sz\u00fcks\u00e9g. Ez a k\u00f3d k\u00e9t \u00f3r\u00e1ig \u00e9rv\u00e9nyes.",
         "access_denied": "Hozz\u00e1f\u00e9r\u00e9s megtagadva",
-        "user_added_pgp_key": "A biztons\u00e1gi be\u00e1ll\u00edt\u00e1sok friss\u00fcltek"
+        "user_added_pgp_key": "A biztons\u00e1gi be\u00e1ll\u00edt\u00e1sok friss\u00fcltek",
+        "frontend_only_user": "Special functions of the frontend"
     }
 }