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/http/package.json

@@ -0,0 +1,28 @@
+{
+  "name": "@tts/http",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    }
+  },
+  "scripts": {
+    "build": "tsc -p tsconfig.json",
+    "typecheck": "tsc -p tsconfig.json --noEmit",
+    "test": "vitest run",
+    "lint": "echo \"no lint configured\""
+  },
+  "dependencies": {
+    "@tts/shared": "workspace:*",
+    "bson": "^7.3.1"
+  },
+  "devDependencies": {
+    "typescript": "^5.7.2",
+    "vitest": "^4.1.10"
+  }
+}