This parameterizes the "make current speaker" and "make last year speaker" function calls and text so there's one less thing to update every year. It then also changes how speaker status works, so that we store actual speaker years in the DB, and only give the special 'speaker' badge to current-year speakers so we don't need to update them.

It also updates a few other other instances of relying on updating the current hardcoded year.

Might be nice to think about a UI to add speakers prior to the year-before-last, but very low priority.

Not tested yet, will ping when I've tested locally. No need to merge imminently, very low benefit from pushing this through quickly. Will want to manually test on the server, should just make sure the Azure Functions server time isn't messed up.

Also intentionally removes the year from the HTML title, it's fine to have that just be "Roguelike Celebration"