fix: only rebuild year info when year has actually changed

[oll3]

Not sure but thought the comparison below looked potentially wrong, where it checks in the month_info year has changed... Shouldn't it check the year_info year instead to decide if it's time to rebuild the year info?

!matches!(&self.month_info, Some(month_info) if month_info.last_year == year)

PR also moves the rebuild of year out from rebuild_inner() since it's only done inside rebuild().