We do have an option to “Create Page from Data” from an App, but not yet the other way
If you have any native Glide tables in your Pages project, you will be able to link those to your App and all basic (non-computed) columns and data in those tables will stay in sync between the two projects. But you will need to recreate any computed columns that you need in your App, and (obviously) build the UI from scratch.
There isn’t a straightforward way to do that. Each would still have it’s own url, but maybe you could do something with a separate website that has automatic redirects based on the user agent…or maybe some domain providers have an option like that??? The easiest would be to just share two separate urls.