feat(web): lighten tabletop scene and tune contact shadows

Replace the dark surface plane with a grey background and a spotlight,
size the contact shadow to the table, and scale its blur and fade with
the shadow plane. Disable depth test on the stacking curve overlay.

apps/web/src/components/viewers/Scene.tsx

@@ -2,7 +2,7 @@ import { Suspense, useEffect, useRef, useState, type ReactNode } from 'react';
 import { Icon } from '@iconify/react';
 import { Canvas } from '@react-three/fiber';
 import { Bounds, ContactShadows, OrbitControls, useProgress } from '@react-three/drei';
-import { Bloom, EffectComposer, Vignette } from '@react-three/postprocessing';
+import { EffectComposer, Vignette } from '@react-three/postprocessing';
 
 /**
  * Shared 3D scene wrapper for object viewers. Provides a consistent camera,
@@ -24,6 +24,7 @@ export default function Scene({
   enablePan = false,
   fullscreen = false,
   overlay,
+  shadowScale = 22,
 }: {
   children: ReactNode;
   autoRotate?: boolean;
@@ -31,6 +32,8 @@ export default function Scene({
   fullscreen?: boolean;
   /** HTML rendered inside the scene container (e.g. controls), shown in fullscreen. */
   overlay?: ReactNode;
+  /** Contact shadow plane size in world units; defaults to a generous 22. */
+  shadowScale?: number;
 }) {
   const containerRef = useRef<HTMLDivElement>(null);
   const [isFullscreen, setIsFullscreen] = useState(false);
@@ -49,7 +52,7 @@ export default function Scene({
   return (
     <div
       ref={containerRef}
-      className="relative h-80 w-full overflow-hidden rounded-lg bg-linear-to-b from-zinc-900 to-zinc-950"
+      className="relative h-80 w-full overflow-hidden rounded-lg bg-linear-to-b from-zinc-300 to-zinc-400"
     >
       <LoadingOverlay />
       {fullscreen && (
@@ -66,7 +69,7 @@ export default function Scene({
       <Canvas
         camera={{ position: [2.2, 1.8, 2.6], fov: 40 }}
         dpr={[1, 2]}
-        gl={{ antialias: true }}
+        gl={{ antialias: true, alpha: true }}
       >
         <ambientLight intensity={0.5} />
         <directionalLight position={[4, 6, 3]} intensity={1.4} />
@@ -78,12 +81,13 @@ export default function Scene({
         </Suspense>
 
         <ContactShadows
-          position={[0, -0.5, 0]}
-          opacity={0.55}
-          scale={8}
-          blur={2.4}
-          far={3}
-          resolution={256}
+          position={[0, -0.01, 0]}
+          opacity={0.2}
+          scale={shadowScale}
+          blur={shadowScale * 0.005}
+          far={shadowScale * 0.01}
+          resolution={1024}
+          color="#000000"
         />
         <OrbitControls
           enablePan={enablePan}
@@ -94,7 +98,6 @@ export default function Scene({
         />
 
         <EffectComposer>
-          <Bloom intensity={0.25} luminanceThreshold={0.85} mipmapBlur />
           <Vignette eskil={false} offset={0.25} darkness={0.6} />
         </EffectComposer>
       </Canvas>