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/components/ui/EmptyState.vue

@@ -3,20 +3,8 @@ withDefaults(defineProps<{ text?: string }>(), { text: "" });
 </script>
 
 <template>
-  <div class="empty">
-    <div class="icon">∅</div>
-    <p>{{ text || $t("common.empty") }}</p>
+  <div class="py-[60px] text-center text-muted/70">
+    <div class="mb-2.5 text-[40px] leading-none">∅</div>
+    <p class="m-0">{{ text || $t("common.empty") }}</p>
   </div>
 </template>
-
-<style scoped>
-.empty {
-  padding: 60px 0;
-  text-align: center;
-  color: var(--mall-faint);
-}
-.icon {
-  font-size: 40px;
-  margin-bottom: 10px;
-}
-</style>