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.

package.json

@@ -42,6 +42,7 @@
     "zod": "^3.25.70"
   },
   "devDependencies": {
+    "@tailwindcss/postcss": "^4.1.11",
     "@types/node": "^24.0.10",
     "@types/react": "19.1.8",
     "@types/react-dom": "19.1.6",
@@ -49,7 +50,7 @@
     "eslint": "^9.30",
     "eslint-config-next": "15.3.4",
     "postcss": "^8",
-    "tailwindcss": "^3.4.15",
+    "tailwindcss": "^4.1.11",
     "typescript": "^5"
   },
   "packageManager": "pnpm@10.12.4",