Record and load client state (Est: 12, Act: 23)
With https://lily.kazv.moe/kazv/libkazv/-/issues/3 this should be easy.
The user should be given the choice to switch account while keeping local data, or to log out of the current session completely.
We might want to use KConfig for storing settings (e.g. last active session). It depends.
When serialization version changes, the client must backup the original data file, allowing the user to revert to the original version if they want. (Bad example: Firefox)