- ArtworkSeedStore now carries the flag; artwork_seeds gains a nullable nameBusy column
(DB v12, migration 11->12) so it survives cold starts with no decode
- resolve() computes the flag from the same bitmap it extracts the colour seed from, so
there is no second decode, and persists it alongside the seed
- overlaidNameBusy reuses the seed job and reads the cached flag synchronously, so the
scrim is known before the art shows; drop the fade
- bottomBandBusy now uses perceptual (gamma-space) luma, edge density and a bright
fraction, which catches busy art on dark backgrounds (issue #40) that mean/variance missed
