chore: update Tailwind CSS from 3.4.15, to 4.1.11

- Changed the PostCSS configuration to use '@tailwindcss/postcss' instead of 'tailwindcss'.
- Deleted the Tailwind configuration file as it is no longer needed.

postcss.config.mjs

@@ -1,7 +1,7 @@
 /** @type {import('postcss-load-config').Config} */
 const config = {
   plugins: {
-    tailwindcss: {},
+    '@tailwindcss/postcss': {},
   },
 };