chore: upgrade Tailwind CSS to v4

- Replace @tailwind directives with @import "tailwindcss"
- Switch PostCSS plugin to @tailwindcss/postcss
- Add @theme inline block mapping CSS vars to v4 theme tokens
- Move accordion keyframes/animations to globals.css
- Remove tailwind.config.ts and tailwindcss-animate (no longer needed)
- Update components.json to clear config path

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

postcss.config.mjs

@@ -1,7 +1,6 @@
 const config = {
   plugins: {
-    tailwindcss: {},
-    autoprefixer: {},
+    "@tailwindcss/postcss": {},
   },
 };