Handle checklist synchronization better for train pass and main tracker

[icykoneko]

I did leave directions, but c'mon, we all know no one reads directions much less follow them.

Since the checklist isn't stored to a server, there would need to be some other method for recording a "pending change" to the local storage which could be detected by other open tabs. I'm concerned about using too much storage though, so maybe timestamping the events, and having them get removed after a short time window might be a solution. Then, if the pending change came from a different tab, it could be sync'd by a interval event - basically mimicing the existing event logic for the user clicking the button.