Allow web upload to remove remote files not present locally

[nellh]

What would you like to see added?

This is similar to #1067 but for web uploads. An option to delete remote files that are not present locally with a confirmation step since this could be destructive.

Alternatives

#1067 would be good to implement as well, some changes since it was originally created have simplified the implementation (such as the simpler bulk delete API that exists now).

Do you have any interest in helping implement the feature?

Yes

Additional information / screenshots

No response