feat: migrate workspace to Tailwind CSS v4 (#377)

* feat: migrate workspace to Tailwind CSS v4

* refactor: move Tailwind v4 setup to CSS directives

packages/ui/package.json

@@ -17,14 +17,13 @@
     "@types/react": "^19.1.2",
     "@types/react-dom": "^19.1.2",
     "@usesend/eslint-config": "workspace:*",
-    "@usesend/tailwind-config": "workspace:*",
     "@usesend/typescript-config": "workspace:*",
     "eslint": "^8.57.1",
     "postcss": "^8.5.3",
     "prettier": "^3.5.3",
     "prettier-plugin-tailwindcss": "^0.6.11",
     "react": "19.1.0",
-    "tailwindcss": "^3.4.1",
+    "tailwindcss": "^4.1.0",
     "typescript": "^5.8.3"
   },
   "dependencies": {
@@ -62,4 +61,4 @@
     "tailwindcss-animate": "^1.0.7",
     "zod": "^3.24.3"
   }
-}
+}