Remember crop area

I've been regularly cropping similar screenshots, screenshots of the application-menu in my case. It would be great if Photos could remember the crop area so we could easily perform similar crop actions.

I understand some crop settings are already stored at `io.elementary.photos.crop-settings`.

Start by locating the handling for the `io.elementary.photos.crop-settings` settings key and the crop interface. Trace how the current crop area is stored and applied, then verify that repeating a similar crop reuses the remembered area and that existing crop behavior still works.

Written by the indexing model from the issue text.