Pair programming is a potential approach if you can’t install any software. You could arrange for one student to drive and the other to navigate. The navigator could use the phone/tablet while the driver uses the laptop to make the app. Students can then switch off for projects.
The Android emulator emulates the entire hardware stack, so it’s not really feasible to have a complete emulator in the browser. There was ARC (Android Runtime for Chrome) which is now part of Chromium and allows for Android apps to run on Chromebooks, but it’s no longer available for PCs, unfortunately.
Our emulator package is just a preconfigured version of the Android Studio emulator with a bit of additional supporting software that facilitates the browser talking to the emulator. If you could at least agree to have your school IT install the Android Studio emulator, we might be able to give you some alternate instructions to bypass the need for the additional software.