chore(dependencies): update Tailwind CSS and related packages for improved styling

- Added @tailwindcss/postcss as a new dependency.
- Updated tailwindcss to version 4.1.11 for enhanced features and performance.
- Upgraded prettier-plugin-tailwindcss to version 0.6.13 for better formatting support.
- Adjusted postcss.config.js to use the new Tailwind CSS plugin structure.
- Removed the obsolete tailwind.config.js file as it is no longer needed.

worklenz-frontend/postcss.config.js

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