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

packages/ui/src/components/VCard.vue

@@ -0,0 +1,14 @@
+<script setup lang="ts">
+const props = withDefaults(defineProps<{ padded?: boolean }>(), { padded: true });
+</script>
+
+<template>
+  <div
+    :class="[
+      'rounded-lg border border-border bg-surface shadow-sm',
+      props.padded ? 'p-5' : '',
+    ]"
+  >
+    <slot />
+  </div>
+</template>