This app was mentioned in 2 comments, with an average of 1.50 upvotes
Probably a program out there that does this for you. All you would need is to install the software on your PC and on your smartphone...
EDiT: 2 seconds of google :
https://play.google.com/store/apps/details?id=de.vrallev.shutdown.android
Of course you can there are multiple tools to control everything on your pc remotely from a full blown remote client to just a small app to turn it off like this one: https://play.google.com/store/apps/details?id=de.vrallev.shutdown.android&rdid=de.vrallev.shutdown.android
or this
https://www.unifiedremote.com/remotes
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