Hide menu button to managers on small screens

This menu isn't rendered in this case, so the "menu" button to toggle it
did nothing.

app/components/layout/admin_header_component.rb

@@ -25,4 +25,8 @@ class Layout::AdminHeaderComponent < ApplicationComponent
         namespaced_root_path
       end
     end
+
+    def show_account_menu?
+      show_admin_menu?(user) || namespace != "management"
+    end
 end