frontend: add management pages

core/frontend/widgets/err_banner.jinja

@@ -7,6 +7,10 @@ Card not registered, or wrong password
 Missing or malformed access code
 {% elif error == 3 %}
 Failed to create user
+{% elif error == 4 %}
+Arcade not found
+{% elif error == 5 %}
+Machine not found
 {% else %}
 An unknown error occoured
 {% endif %}