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/admin/pages/login.vue

@@ -37,54 +37,24 @@ async function submit(): Promise<void> {
 </script>
 
 <template>
-  <div class="login-shell">
-    <form class="card form-narrow login-card" @submit.prevent="submit">
-      <p class="eyebrow">{{ $t("common.appName") }} · Admin</p>
-      <h1 class="page-title">{{ $t("auth.welcome") }}</h1>
-      <p class="muted">{{ $t("admin.dashboardTitle") }}</p>
-      <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>
-      <p v-if="errorMessage" class="error-text" role="alert">{{ errorMessage }}</p>
-      <button class="btn primary submit-button" type="submit" :disabled="loading">
-        {{ loading ? $t("common.loading") : $t("common.login") }}
-      </button>
-      <p class="muted hint">{{ $t("auth.adminHint") }}</p>
+  <div class="grid min-h-screen place-items-center bg-bg px-6 py-8 font-sans text-text">
+    <form class="w-full max-w-[420px]" @submit.prevent="submit">
+      <VCard>
+        <p class="mb-2 text-xs font-bold uppercase tracking-[0.08em] text-primary">{{ $t("common.appName") }} · Admin</p>
+        <h1 class="mb-2 text-xl font-bold">{{ $t("auth.welcome") }}</h1>
+        <p class="mb-5 text-sm text-muted">{{ $t("admin.dashboardTitle") }}</p>
+        <VField :label="$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>
+        <p v-if="errorMessage" class="my-2 text-sm text-danger" role="alert">{{ errorMessage }}</p>
+        <VBtn class="w-full" variant="primary" type="submit" :disabled="loading">
+          {{ loading ? $t("common.loading") : $t("common.login") }}
+        </VBtn>
+        <p class="mt-4 text-center text-xs text-muted">{{ $t("auth.adminHint") }}</p>
+      </VCard>
     </form>
   </div>
 </template>
-
-<style scoped>
-.login-shell {
-  min-height: 100vh;
-  display: grid;
-  place-items: center;
-  padding: 24px;
-}
-.login-card {
-  width: min(100%, 420px);
-  margin: 0;
-}
-.eyebrow {
-  color: var(--primary);
-  font-size: 13px;
-  font-weight: 700;
-  letter-spacing: 0.08em;
-  margin: 0 0 10px;
-  text-transform: uppercase;
-}
-.submit-button {
-  width: 100%;
-  justify-content: center;
-}
-.hint {
-  font-size: 12px;
-  margin: 16px 0 0;
-  text-align: center;
-}
-</style>