Feature: Enable/disable URLs from the list of XiOSK pages

**What feature would you like to see?**
I think it might be interesting to have a way to disable a page from the list of the pages... this would prevent me of deleting it, and add it again when I want it back.

**Why is this feature useful or needed?**
I'm starting to use XiOSK with 2 differents [ShowGo](https://github.com/puckawayjeff/showgo/tree/main) slideshows (they are the best photos of very different road trips).
I want to switch from one slideshow to another on different occasions.

**How do you imagine it working?**
Maybe having an enabled icon beside the "X" in the XiOSK interface. Another way would be to allow duration to be zero.

That would change the /opt/xiosk/config.json, either by adding a new variable or by allowing the duration to be 0.

Start by inspecting /opt/xiosk/config.json and the XiOSK management interface, since these are the only implementation locations named in the issue. Trace how pages are listed, removed, and selected, then define completion as allowing a configured page to be disabled and re-enabled without deleting it; no test file is mentioned, so add or run the relevant project checks you find.

Written by the indexing model from the issue text.