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/tailwind.config.js

@@ -1,8 +0,0 @@
-/** @type {import('tailwindcss').Config} */
-module.exports = {
-  content: ['./src/**/*.{js,jsx,ts,tsx}'],
-  theme: {
-    extend: {},
-  },
-  plugins: [],
-};