fix: Remove autoprefixer from PostCSS config

- autoprefixer not installed and not needed for Tailwind 4
- Tailwind 4 includes autoprefixing built-in
- Fixes: Cannot find module 'autoprefixer'

postcss.config.cjs

@@ -1,6 +1,5 @@
 module.exports = {
   plugins: {
-    tailwindcss: {},
-    autoprefixer: {},
-  },
+    tailwindcss: {}
+  }
 };