Stellarium/stellarium ? reverse-engineered prompt

Build me a desktop planetarium app that shows a realistic night sky in real time, like Stellarium does.

I want to be able to open it and immediately see the sky from any location and time, then move around the sky smoothly, zoom in on stars, planets, the Moon, and deep sky objects, and get clear labels and basic info when I click things. It should look polished and feel like a real astronomy tool, not a game, with accurate lighting, atmospheric effects, constellations, and a nice 3D view of the horizon and landscape.

Please make it work as a cross platform app and keep it easy to build and run from source. If you need current docs or libraries, look them up online. Also include a simple way to change date, time, and observing location, plus a few default sky scenes so it feels good right away.