FROM POLL: Watched list behavior

Change the Watched list so that it includes anything the user has watched at least once, regardless of its current tracking status.

This means an item can appear in multiple lists at the same time. For example, a movie that has previously been watched but is now added to Planning for a rewatch would appear in both Watched and Planning.

Discord poll result: 17 votes (100%) supported this change. https://discord.com/channels/1504625861146443897/1513318496753156115/1516394463365300345