Sort by similarity in volume overview #1560

A user requested to be able to sort files by similarity in the volume overview 8similar to sorting in largo, #1557).

This would mean that we have to compute feature vectors for all images and videos, too. There already is the "sort by color" option that does a similar thing. Sorting by feature vector could definitely replace this but do we want to add ~10M feature vectors to the DB "just" for this sorting feature? Are there other use cases for whole-file feature vectors?