site: use postcss-preset-env and cssnano

site/.postcssrc.json

@@ -1,3 +1,6 @@
 {
-  "plugins": {}
+  "plugins": {
+    "postcss-preset-env": {},
+    "cssnano": { "preset": "default" }
+  }
 }

site/package.json

@@ -20,6 +20,7 @@
     "@sveltejs/adapter-auto": "^6.1.1",
     "@sveltejs/kit": "^2.43.2",
     "@sveltejs/vite-plugin-svelte": "^6.2.0",
+    "cssnano": "^7.1.1",
     "hast-util-to-html": "^9.0.5",
     "hastscript": "^9.0.1",
     "mdast": "^2.3.2",
@@ -27,6 +28,7 @@
     "mdast-util-to-hast": "^13.2.0",
     "mdast-util-toc": "^7.1.0",
     "mdsvex": "^0.12.6",
+    "postcss-preset-env": "^10.4.0",
     "prettier": "^3.6.2",
     "prettier-plugin-svelte": "^3.4.0",
     "rehype-autolink-headings": "^7.1.0",