Calendar export should filter on schedule items, not programs

[japsu]

Calendar export is invoked from a view that only shows schedule items matching current filters:

The filters (in this case show only favorites and hide past programs) are passed to the calendar export.

However, the export filters program items with the same filters and then includes all schedule items of matching program items.

But a program item may have multiple schedule items, some of which may not pass the current filters even though their parent program items do:

In this case, I also get the Saturday run of this workshop in my calendar despite expecting to only get the Sunday one.