Add option to remove write access on disk after uploadToPaths

[fm3]

On instances with deletion disabled and uploadToPaths configured to local disk, it would be nice to offer a measure to prevent accidental deletion. When finishUploadToPaths is called, wk could run chmod or an equivalent on the files.

We need to make sure that wk runs as a user with permissions to do this, though.

Compare https://scm.slack.com/archives/C03B6160ATY/p1761905190567599?thread_ts=1761812606.756719&cid=C03B6160ATY