Fix category prefetch in Story.get_main_stories - #258
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The prefetch queryset excluded categories whose direct image field was
blank, leaving story.category as None even though category images live
on the CategoryImage relation. It also used .only("id") which triggered
a deferred-field query per story when category fields were accessed.
Prefetch categories unfiltered with their active images, and make
Category.get_first_image use the prefetched images when available so
rendering featured stories does no per-story queries.
- Select related org on the prefetched category queryset - Simplify Category.get_first_image and document the prefetched_images contract - Test that inactive category images are ignored and the lowest-id active image is used
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The category prefetch in
Story.get_main_storiesfiltered on the category's directimagefield — which is normally blank, since category images live in the related CategoryImage model — sostory.categoryprefetched to None for most stories and category images never rendered. The.only("id")restriction also triggered a deferred-field query per story.The prefetch no longer filters categories (inactive handling already lives in
get_category_image) and instead prefetches active category images into a cache thatget_first_imagenow uses. A test covers the blank-image-field case and locks in the query count withassertNumQueries.