Fix CI and restore Tailwind v4 styles

Co-authored-by: huangyiirene <7665279+huangyiirene@users.noreply.github.com>

Author: Copilot

apps/site/app/global.css

@@ -1,3 +1 @@
-@tailwind base;
-@tailwind components;
-@tailwind utilities;
+@import "tailwindcss";