chore(tailwind): setup Tailwind CSS with preflight on

- Install tailwindcss, postcss, autoprefixer
- Add tailwind.config.js and postcss.config.js
- Create src/styles/tailwind.css with base/components/utilities
- Import Tailwind before index.css in main.tsx

postcss.config.js

@@ -0,0 +1,7 @@
+export default {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+}
+