Potential bug in month calculation

I believe this should be `Local.ymd(year + 1, 1, 1).and_hms(0, 0, 0)` instead as right now it seems as if we're getting the entire month of december + (almost) the entire first day of January.

https://github.com/cthit/hubbit/blob/f4b1805928e2a9d856f58def8ef919ea51c80af8/backend/src/services/stats/util.rs#L95C1-L96C1