UI not updated after playlist deletion

[orontee]

Describe the bug
Deletion of a playlist removes the corresponding .m3u8 file but the playlist is still displayed in the UI.

To Reproduce

1. Create a playlist with local files : a .m3u8 file is created under /var/lib/mopidy/m3u or equivalent
2. Right click on the play list to open its contextual menu
3. Select "delete"
4. The .m3u8 file is deleted but the playlist is still there in the UI

Expected behavior

I expect the playlist to be removed from the UI.

Screenshots
[If applicable, add screenshots to help explain your problem.]

Environment details:

• OS: Debian 11
• Browser: Firefox
• Iris version: 3.58.0

Additional context
One can delete the playlist from the page displaying the playlist content. An analogous bug happens when deleting from there: The UI is not updated and the browser isn't redirected to another page (which one?).

[jaedb]

This is a see-saw bug that is caused by #678 by not removing the deleted playlist from the app state, nor redirecting.

[jaedb]

The playlist is removed from the library, but remains in the local (browser) database. This is to ensure that Spotify playlists can be 'undeleted' (which is effectively just re-following it). Returning to the library will show it is now removed, but you can still revisit it by using Back in the browser window.

A solution I think will serve both scenarios is keeping it as-is, but flagging the playlist as deleted so it is clear that the playlist on screen has been deleted.