Feature request: sort by file size

I would like to have a filter which shows me downloaded podcast episodes from largest to smallest file size. This would require the "Sort By" feature to include "Smallest to largest (filesize)" and "Largest to smallest (filesize)".

Start by locating the podcast episode list and its existing "Sort By" feature, then trace how downloaded file sizes are exposed. Add "Smallest to largest (filesize)" and "Largest to smallest (filesize)" sorting, and verify that downloaded episodes appear in the requested order.

Written by the indexing model from the issue text.