Detect orphaned projects #1008
Description
If some projects in the list of local projects do not exist in Mergin anymore, the app does not indicate that in any way. Also, checking project status will only say "no changes".
It would be good to show some kind of warning icon next to the project name in the list. Clicking the warning icon would tell the user that the project does not exist anymore. And maybe later we could offer an option to create a new project and upload the content to "rescue" such project.
Slightly related to #379 as the warning icon could reuse the same icon area as "sync" icon would normally do...