Preserve state and restore upon revisit

[reefdog]

If the visitor closes the browser and returns on the same machine, we should recreate their last state as closely as possible: time interval, selected entity (if it still exists on the current interval), etc. Ideally this state would be reflected in the URL so it would be sharable.

Eventually, if we add user accounts, this state should be stored on the user account so it would persist across devices.