Added Sass to container

AGENTS.md

@@ -194,5 +194,9 @@ except `public/cache/*` and `novaconium/contact-log.txt`.
   `App/css/main.css` (project-owned; docker-compose mounts `App/css` to
   the container's `public/css`, and it's served at `/css/main.css`):
   `sass --load-path=App/sass --load-path=novaconium/sass/defaults --no-source-map novaconium/sass/main.sass App/css/main.css`
-  — commit the regenerated CSS. See `/admin/docs/styling` for a Docker
-  fallback if `sass` isn't installed locally.
+  — commit the regenerated CSS. The Docker image ships Dart Sass standalone
+  (pinned `DART_SASS_VERSION` in the `Dockerfile`, symlinked to
+  `/usr/local/bin/sass`), so the same command runs inside the container;
+  bump that version deliberately, like the PHP base tag. See
+  `/admin/docs/styling` for the Docker fallback if `sass` isn't installed
+  locally.