If only the app could be stored on the router.

Unfortunately the only tech stack that can do this is the web, (serial/remote shell comes close).

In fact I regard this as the major failure of the app method of program deliverance. Why do you need to install them at all? It should be like the web, hit an address load the app. It is why I am thankful that the web was not developed as a commercial project. No for-profit entity would have let it escape their control like that. It would have been designed exactly like the app system for phones is. enforced central blessed "app-stores" and manual install processes.