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/shop-admin/pages/login.vue

@@ -27,21 +27,21 @@ async function submit(): Promise<void> {
 </script>
 
 <template>
-  <main class="page">
-    <form class="card form-narrow" @submit.prevent="submit">
-      <h1 class="page-title">{{ $t("auth.welcome") }}</h1>
-      <div v-if="error" class="error-text" role="alert">{{ error }}</div>
-      <div class="field">
-        <label for="email">{{ $t("common.email") }}</label>
-        <input id="email" v-model="email" type="email" autocomplete="username" required />
-      </div>
-      <div class="field">
-        <label for="password">{{ $t("common.password") }}</label>
-        <input id="password" v-model="password" type="password" autocomplete="current-password" required />
-      </div>
-      <button class="btn primary" type="submit" :disabled="busy">
-        {{ busy ? $t("common.loading") : $t("common.login") }}
-      </button>
-    </form>
+  <main class="grid min-h-screen place-items-center bg-bg px-4 font-sans text-text">
+    <VCard class="w-full max-w-[420px]">
+      <form @submit.prevent="submit">
+        <h1 class="mb-5 text-xl font-bold text-text">{{ $t("auth.welcome") }}</h1>
+        <div v-if="error" class="my-2 text-sm text-danger" role="alert">{{ error }}</div>
+        <VField :label="$t('common.email')">
+          <VInput id="email" v-model="email" type="email" autocomplete="username" required />
+        </VField>
+        <VField :label="$t('common.password')">
+          <VInput id="password" v-model="password" type="password" autocomplete="current-password" required />
+        </VField>
+        <VBtn variant="primary" type="submit" :disabled="busy">
+          {{ busy ? $t("common.loading") : $t("common.login") }}
+        </VBtn>
+      </form>
+    </VCard>
   </main>
 </template>