Timed Undo for History Deletion

[lk340]

History deletion is currently implemented such that past chats are immediately removed forever. Users should have an "Undo" option after they delete chat history to give them time to undo deletion. Some things to keep in mind:

• Adding something like a simple 3-second timer wouldn't be a good enough solution, as it wouldn't account for edge cases, like not having the chance to undo deletion if the history view is immediately closed.
• Consider something like marking deleted chat objects with recentlyDeleted and then cleaning them up every 24 hours.

[timlenardo]

Design here!