fix(seasonal): Halloween fog layers drop willChange under reduced motion

The three fog bands pinned compositor layers even when their animation was
'none' (always the case in the settings swatch). Match the sibling layers.

Fixes #73

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/components/seasonal/themes/Halloween.tsx

@@ -164,7 +164,7 @@ export function HalloweenOverlay({ reduced }: SeasonalOverlayProps) {
               height: `${f.height}px`,
               backgroundImage: `radial-gradient(60% 100% at 50% 100%, ${FOG_TINT} 0%, transparent 75%)`,
               filter: 'blur(14px)',
-              willChange: 'transform, opacity',
+              willChange: reduced ? undefined : 'transform, opacity',
               opacity: reduced ? 0.5 : undefined,
               transform: reduced ? 'translate3d(2%, 0, 0) scale(1.18)' : undefined,
               animation: reduced