Contracts can't really shield from that kind of negligence either though. You can't have someone sign a contract indemnifying you from everything and then have no culpability when you literally poison them.

I get that servers have to deal with selective gluten allergies but nut and dairy allergies are not that. They are deadly and the server/kitchen should have absolutely refused to serve any food they couldn't separate. This is basic knowledge in the food industry too, something they should have known and been trained on.