fix(web): resolve Payload CMS build error with Node.js ESM loader

Payload CMS imports .css/.scss/.svg files that Node.js ESM can't handle
during page data collection. Added a custom ESM loader that stubs these
asset imports, fixing the build that has been broken since the upgrade.

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

apps/web/package.json

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