fix(web): add CSS stub loader for Payload CMS route collection in Docker

Node ESM can't handle .css imports during Next.js route collection.
This loader intercepts .css resolutions and returns empty modules,
fixing the build for all Payload deps (richtext-lexical, react-image-crop, etc.)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/next.config.ts

@@ -89,6 +89,8 @@ const config: NextConfig = {
     "@payloadcms/db-sqlite",
     "@payloadcms/richtext-lexical",
     "@payloadcms/next",
+    "@payloadcms/ui",
+    "react-image-crop",
     "sharp",
   ],
   turbopack: {