fix(web): use --import instead of --experimental-loader for Vercel compat

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/css-stub-register.mjs

@@ -0,0 +1,3 @@
+import { register } from "node:module";
+import { pathToFileURL } from "node:url";
+register("./css-stub-loader.mjs", pathToFileURL("./"));

apps/web/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "build": "NODE_OPTIONS='--experimental-loader ./css-stub-loader.mjs' next build --webpack",
+    "build": "NODE_OPTIONS='--import ./css-stub-register.mjs' next build --webpack",
     "clean": "git clean -xdf .cache .next .turbo node_modules",
     "dev": "next dev",
     "format": "prettier --check . --ignore-path ../../.gitignore",