Option to abort (image) syncing

It would be nice to have an option to cancel the image syncing process. At my mobile the first initial sync takes up to 20 minutes. If i am just testing something, i would want to cancel it.

Maybe we can add an option to cancel to the notification?

Start by locating the image syncing process and the notification associated with the initial sync; the issue does not name files, tests, or entry points. The work is done when a user can cancel an in-progress sync, including from the notification, without leaving the app in an incomplete state.

Written by the indexing model from the issue text.