Make RollupMapper calendar windows DST-aware

### Body `RollupMapper` with a `DayWindow` always expects 24 hourly keys, so a local-timezone upstream mapper breaks on DST days: spring-forward (23h) leaves one expected key that never arrives and the run is held forever; fall-back (25h) drops the extra hour's events. Current workaround (in the partition docs / known limitations): use UTC partition keys. This tracks making the calendar windows DST-aware so the expected key set matches the real number of hours, instead of relying on a UTC workaround. related #64571. ### Committer - [x] I acknowledge that I am a maintainer/committer of the Apache Airflow project.