chore(dependencies): update Tailwind CSS and related configurations

- Removed @tailwindcss/postcss from devDependencies and updated tailwindcss to version 3.4.15 for improved styling.
- Added autoprefixer as a new dependency to enhance CSS compatibility.
- Updated postcss.config.js to reflect the new Tailwind CSS plugin structure.
- Created a new tailwind.config.js file to define Tailwind's configuration.
- Adjusted CSS imports in index.css to utilize Tailwind's utility classes.
- Refined focus styles across various components for better accessibility and visual consistency.

worklenz-frontend/package.json

@@ -60,7 +60,6 @@
     "worklenz": "file:"
   },
   "devDependencies": {
-    "@tailwindcss/postcss": "^4.1.11",
     "@testing-library/jest-dom": "^6.6.3",
     "@testing-library/react": "^16.3.0",
     "@testing-library/user-event": "^14.6.1",
@@ -74,10 +73,11 @@
     "@types/react-dom": "19.0.0",
     "@types/react-window": "^1.8.8",
     "@vitejs/plugin-react": "^4.3.4",
+    "autoprefixer": "^10.4.21",
     "postcss": "^8.5.2",
     "prettier-plugin-tailwindcss": "^0.6.13",
     "rollup": "^4.40.2",
-    "tailwindcss": "^4.1.11",
+    "tailwindcss": "^3.4.15",
     "terser": "^5.39.0",
     "typescript": "^5.7.3",
     "vite": "^6.3.5",