refactor: share trace, error boundary, and proxy http helpers

Lift the trace-to-shape geometry into @tts/mesh (traceToShape/
traceToUvBounds), parameterized by scale so the web token viewer and
@tts/tabletop share one implementation. Move the CORS proxy HTTP helpers
(assetUrl, resolveAssetUrl, traceImage) into a new @tts/http package, and
make @tts/tabletop's ErrorBoundary the single source used by the web app.

This removes the duplicated ErrorBoundary, assetUrl, tabletopHttp, and
trace-to-shape code from apps/web and packages/tabletop.

packages/mesh/src/index.ts

@@ -2,4 +2,5 @@ export * from './types.js';
 export * from './shapes.js';
 export * from './tessellate.js';
 export * from './walls.js';
-export * from './extrude.js';
+export * from './extrude.js';
+export * from './trace.js';