✨ Add 401 page (#1508)

public/locales/en/layout/errors/access-denied.json

@@ -0,0 +1,5 @@
+{
+  "title": "Access denied",
+  "text": "You do not have sufficient permissions to access this page. If you believe, that this is not intentional, please contact your administrator.",
+  "switchAccount": "Switch to a different account"
+}