chore: add @tailwindcss/postcss and PostCSS setup for Tailwind v4

plugins/piniaPersistedState.client.ts

@@ -0,0 +1,7 @@
+import { defineNuxtPlugin } from "#app";
+import { createPersistedState } from "pinia-plugin-persistedstate";
+
+export default defineNuxtPlugin((nuxtApp) => {
+  // Register persisted state plugin for Pinia on client
+  nuxtApp.$pinia.use(createPersistedState());
+});