- Introduced `recalculateActivity` method in `Meetup` model to centralize activity and event timestamp updates.
- Added `MeetupEventObserver` to trigger activity recalculation on event save/delete.
- Updated `/meetups:update-activity` command to leverage the new model method for cleanup.
- Enhanced tests to cover various `MeetupEvent` scenarios affecting activity states.
HolgerHatGarKeineNode