Relocate the image-upload service from core to core/artwork as
artwork.Uploader, co-locating it with the resolver/worker/serving that own
the artwork state it invalidates. MaxImageUploadSize moves too — its only
callers are the two image-upload handlers — which lets core/image_upload.go
be deleted entirely.
Extract the shared "clear resolved state + re-queue at Bump" invalidation
into artwork.Refresh and fold nativeapi's refreshArtwork handler onto it,
removing the duplicated DeleteForItem+Enqueue block that had drifted into
three places.
The wire provider moves from core's set to artwork's; the
playlists.ImageUploadService binding moves to the top-level injector so
core/artwork stays unaware of playlists. Behavior is unchanged.
