fix: add tailwindcss as devDependency for Nuxt UI v3

@nuxt/ui provides the Vite plugin but tailwindcss package itself
must be installed for @import "tailwindcss" to resolve in CSS.

package.json

@@ -24,6 +24,7 @@
     "vue-router": "latest"
   },
   "devDependencies": {
+    "tailwindcss": "^4.2.2",
     "typescript": "~5.8.0"
   },
   "pnpm": {

pnpm-lock.yaml

@@ -36,6 +36,9 @@ importers:
         specifier: latest
         version: 5.0.4(@vue/compiler-sfc@3.5.32)(vue@3.5.32(typescript@5.8.3))
     devDependencies:
+      tailwindcss:
+        specifier: ^4.2.2
+        version: 4.2.2
       typescript:
         specifier: ~5.8.0
         version: 5.8.3