This is a good idea. Just heat shrink a wire inside with the cable. Cut the wire, trigger the alarm. Could run on a 9V battery hidden inside the locking mechanism. The circuitry would be really simple... hmmm.Something that makes noise. Maybe a cable and when the circuit gets broken by cutting or pulling apart, by a thief, it sounds off.
That style lock used to be used ay stores selling electronics or expensive goods.
Sounds complex and spendy, doesn’t it?
edit for an afterthought