Add undo/revert to manage tags dialog

The manage tags dialog shows apply and cancel buttons with more than one file selected. You can undo any deletions/adds by hitting cancel.

With only one file selected, there is no way to revert changes, it takes effect immediately. The only thing you can do is toggle "show deleted" and hope you can find the tag you changed. (difficult if you click something accidentally)

Please provide an undo feature for the manage tags dialog (to undo the last change made whether it's adding or deleting a tag) or a way to restore the state before you started making changes (perhaps a revert button on the dialog?), similar to what happens if you select cancel when editing multiple files' tags.

Start by locating the manage tags dialog and compare its single-file behavior with the existing multi-file apply/cancel flow. Decide whether the issue's undo-last-change or restore-before-editing behavior fits the dialog, then verify that additions and deletions can be reverted without relying on the “show deleted” toggle.