v3.21.184

Custom palette: background gradient + crest watermark (club-branded look)

Add gradient_from/gradient_to (+ angle) and a background_image watermark
(opacity/size) to the custom palette, applied via the shared .hero-bg layer so
every card can have a red-gradient + faint crest look. Editor fields under the
advanced custom section; pure buildGradient helper + test; visual snapshot.