fix: use cssnano for CSS minification via PostCSS, bypassing Parcel optimizer segfault

- add cssnano to .postcssrc for in-pipeline minification (keeps Tailwind and comment stripping)
- update build process to skip Parcel's --minify step, avoiding lightningcss crash on Node 22/Linux
- ensures Vercel and local builds both produce minified CSS without breaking Tailwind

Author: nweii

.postcssrc

@@ -1,6 +1,7 @@
 {
   "plugins": {
     "postcss-discard-comments": { "removeAll": true },
-    "@tailwindcss/postcss": {}
+    "@tailwindcss/postcss": {},
+    "cssnano": { "preset": ["default", { "discardComments": { "removeAll": true } }] }
   }
 }