Building on what Tom J Nowell said in his comment you can't directly integrate it. I'd say your only (although hacky) way of achieving something close to this is a custom template with an iframe.
You just create a new page. Then you need a Custom Page Template. You have two options, either a Custom Page Template or a Specialized Page Template.
Inside this template it depends if you want header, menu and footer of your site or you don't. Say you only want the app without any site navigation just put an iframe in this template and be done.
<iframe src="http://url-of-your-app.tld" />
You'll probably need some more CSS to make the iframe fullscreen but I think you get the general idea. Let me know if you need more detailed directions.