Improve save public list

[slothful-vassal]

This pull request referenced to the problems mentioned in https://github.com/Flomp/wanderer/issues/430#issuecomment-3237800669

What have I done:

• after publishing a trail, the user was asked again to publish the trails when he save further changes to the list without leaving the list view page before -> ask only once
• asking for publishing all trails only when there are private trails in the list
• show loading indicator when publishing a list
• replace the 'public' toggle -> use same toggle already used in trail edit page
• adds the possibility to keep private trails private

The last point may be the most controverse one. I have seen, that it is possible to add private trails to an existing public list, eg from trails view. So in my opinion, you should be able to in list edit view too.

I hope, this PR is not too intrusive.