MVP networked session

Given the following:

* A static scene
* An HTTP server

The following needs to happen:

* [ ] Extend the HTTP server to handle a WebSocket connection
* [ ] Extend the scene to handle a dynamic list of users with camera information
* [ ] Add a local user to the scene
* [ ] Render said dynamic list of users
* [ ] Synchronise the initial state when one connects
* [ ] Add a remote user to the scene as the "server"
* [ ] Add a remote user to the scene as the "client" in the browser
* [ ] Remove a disconnected user from the scene

Start by locating the existing HTTP server and static scene entry points. Trace how scene users and camera information are represented, then define the WebSocket connection and synchronization flow; done means connected clients see local and remote users, initial state is synchronized, and disconnected users are removed.

Written by the indexing model from the issue text.