Client doesn't save/backup trade state

[f321x]

The current client implementation does not save any state in a db (purely in memory), this would cause a running trade to fail if the trader closes the application. To make it practical for use it would be necessary to save state so the trade can be continued later (e.g. after waiting for a taker to accept the offer).
This could be done by integrating with existing robosats infrastructure or creating API endpoints on the coordinator to store and request data encrypted. Browser cache is probably impossible as the Tor browser deletes most of the cache upon restart.