Generate link of the scene

- the current scene should be saved
- a url with a unique id should be generated upon request from the user using the button in the top right corner
- that url should allow the user to resume the scene
- inform the user for how long the scene would be available (to be discussed with the lab, I guess we don't want to save scenes and store them forever).

Start by locating how the current scene is represented and where the top-right button actions are handled. Trace how a saved scene could be retrieved from a unique URL so the user can resume it. Before implementation, confirm the scene retention period with the lab; done means a requested link saves the scene, opens it again, and communicates its availability period.

Written by the indexing model from the issue text.