Fix DST drift in occurrence generation

- Occurrence.generate_dates: use ChaosCalendar::occurrences_for_timezone
  with Time.zone.tzinfo.identifier — occurrences now keep wall-clock
  time across DST boundaries (19:00 stays 19:00 in summer and winter);
  requires chaoscalendar gem with occurrences_for_timezone support
  (Gemfile.lock bumped accordingly)
- Occurrence.find_in_range: joins(:event) inner join excludes occurrences
  whose event no longer exists (107k orphaned rows from the pre-revival
  calendar era were purged from the test DB); includes(:node) retained
  for eager loading; column references qualified with table name

0 files changed, 0 insertions, 0 deletions