expand_rrule reused dtstart's raw UTC time-of-day for every occurrence,
so a weekly meeting spanning a DST transition (e.g. created in winter
CST, recurring into summer CDT) drifted an hour once displayed in the
machine's local timezone.
Rewrites occurrence generation on chrono's Local/NaiveDate (already a
transitive dependency via sqlx, now promoted to direct) instead of
hand-rolled epoch-day arithmetic: each occurrence keeps dtstart's local
wall-clock hour/minute, re-resolving the UTC offset per occurrence date
so DST is applied correctly for that specific day. civil_from_days/
weekday_from_epoch_day/is_leap_year/days_in_month are no longer needed
(chrono's NaiveDate replaces them) and are removed.
iamdoubz
6f07f28cef