Add track filtering

[zaknesler]

For any transfers (but it makes the most sense for playlist-to-playlist), I'd like to be able to add a filter (e.g. where year >= 2023) to move to another playlist.

A more detailed example would be transferring "My Shazam Tracks" to a "2023" playlist, where you disable removing from the Shazam playlist, and instead just copy all tracks Shazamed since 2023.

Can probably just store these as JSON on the watchers table.