feat(ui): adopt Tailwind v4 design system and archive change

- Add tailwindcss v4 + @tailwindcss/vite to mall, shop-admin, admin
- Add @vmall/shared/theme.css tokens with html[data-accent] presets
- Add @vmall/ui kit (VBtn/VBadge/VField/VInput/VCard/VPanel/VTable/VPage,
  VAccentSwatch, useAccent) as a Nuxt module
- Convert all three apps to kit + utilities; delete ui.css/mall.css and
  every <style scoped>; consoles get accent presets, mall locked to red
- Fix VCard boolean prop default (padding) and PDP/store stale
  useAsyncData keys on param navigation
- Archive adopt-tailwind-design-system; new frontend-ui capability spec

apps/mall/app.vue

@@ -1,13 +1,20 @@
 <script setup lang="ts">
 const session = useSessionStore();
+
+useHead({
+  htmlAttrs: {
+    "data-accent": "red",
+  },
+});
+
 onMounted(() => session.hydrate());
 </script>
 
 <template>
-  <div>
+  <div class="flex min-h-screen flex-col bg-bg font-sans text-text">
     <ShellTopBar />
     <ShellSiteHeader />
-    <main class="mall-main">
+    <main class="flex-1">
       <NuxtPage />
     </main>
     <ShellSiteFooter />