feat: simple-sync

[Pertempto]

Add simple-sync integration to allow the user to sync records between devices.

1. Host paid back end
2. Allow user to self host (we just need a setting to allow the user to configure the URL for their simple sync server)
3. Update data management to event based system
4. Create system to easily import existing local data to new back end
5. Add UI to easily authenticate with simple sync

[Pertempto]

@JCampana98 I hope to start on this one this winter. Simple sync isn't quite ready for production usage yet, but I'm making rapid progress.

[Pertempto]

Blocked by kwila-cloud/simple-sync#42