build: upgrade Tailwind CSS from v3 to v4

- Migrate from Tailwind CSS 3.x to 4.1.15
- Replace autoprefixer with @tailwindcss/postcss 4.1.15
- Update PostCSS configuration for Tailwind v4 compatibility
- Convert globals.scss to globals.css for CSS-first configuration
- Remove legacy tailwind.config.cjs in favor of CSS-based config
- Update all component imports to use new globals.css
- Remove old.tsx.disabled file

package.json

@@ -32,6 +32,7 @@
     "zod": "^4.1.12"
   },
   "devDependencies": {
+    "@tailwindcss/postcss": "^4.1.15",
     "@testing-library/jest-dom": "^6.9.1",
     "@testing-library/react": "^16.3.0",
     "@types/node": "^24.9.1",
@@ -40,14 +41,13 @@
     "@typescript-eslint/eslint-plugin": "^8.46.2",
     "@typescript-eslint/parser": "^8.46.2",
     "@vitest/ui": "^3.2.4",
-    "autoprefixer": "^10.4.7",
     "eslint": "^9.38.0",
     "eslint-config-next": "15.5.6",
     "happy-dom": "^20.0.8",
     "postcss": "^8.4.14",
     "prettier": "^3.6.2",
     "prettier-plugin-tailwindcss": "^0.7.1",
-    "tailwindcss": "^3.2.0",
+    "tailwindcss": "^4.1.15",
     "type-fest": "^5.1.0",
     "typescript": "^5.9.3",
     "vitest": "^3.2.4"