Realtime sync

[ellie]

Currently, regardless of whether the sync daemon is in use, Atuin syncs on a schedule. With the daemon this is regardless of input, but without it it's driven by shell usage.

Opening this to track the possibility of syncing in realtime. Records could be pushed up to the server as it happens, and instantly broadcast to all other online machines.

This means that when switching machine, the user immediately has the setup they may expect, rather than having to wait a certain interval for it to appear.