Restaurants are upping security after The Post sent an underage intern around to 30 bars in the East Village to see if he’d be carded. Eater.com reports that Stephen Hanson, owner of B.R. Guest (Dos Caminos, Ruby Foo’s), has been sending underage kids to his places to make sure his staff is check ing IDs — and firing them if they don’t. Hanson tells Page Six, “We gave each bartender a letter saying they understand how serious underage drinking is, and had them sign it. It also says if we did send spotters or underage kids in and they serve them, they would be terminated.”