We need to be able to lock files so they don't get deleted from the catalog

Often clients want a few low res images immediately after the shoot (for social media, etc.) and I'll deliver these immediately. Then, later that week I will edit the whole job for final delivery as carefully culled and edited high res files.

I live in fear that when I come back and edit I will cull from the final edit an image I've already shown to the client as a low res file.

I would love a feature that allows me to lock an image from being deleted (or marked x) from the catalog. Something to make sure that image is protected.

Yes I could give it five stars or mark it a particular color, but ratings and colors are something that I could easily change during the culling process. I want something like a LOCK where you have to go and affirmatively UNLOCK before further changing anything about or moving the image.