Add 3D object viewers with r3f stack

Add per-class 3D viewers for tiles, tokens, cards, and custom models
using React Three Fiber, drei, and postprocessing. Viewers are
lazy-loaded and registered through the existing viewer registry, with a
shared scene wrapper for lighting, orbit controls, and subtle effects.

Add a CORS-safe /asset proxy route so three.js loaders can fetch
Workshop-hosted textures and models, and extend TTSObject with the
CustomMesh and CustomTile/CustomToken fields the viewers read.

apps/web/vite.config.ts

@@ -10,6 +10,7 @@ export default defineConfig({
       '/search': 'http://localhost:3000',
       '/items': 'http://localhost:3000',
       '/health': 'http://localhost:3000',
+      '/asset': 'http://localhost:3000',
     },
   },
 });