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

openspec/specs/frontend-admin/spec.md

@@ -2,9 +2,7 @@
 
 ## Purpose
 The platform console for managing users, shops and currencies.
-
 ## Requirements
-
 ### Requirement: Platform user and shop management
 Platform admins SHALL assign user roles (with shop scope), create shops, and suspend/activate shops. Suspended shops' products MUST NOT be purchasable (enforced by API, reflected in UI).
 
@@ -29,3 +27,18 @@ Platform admins SHALL manage points products and inspect and fulfill redemption
 #### Scenario: points mall appears in admin navigation
 - **WHEN** an authenticated platform admin opens the admin console
 - **THEN** points-product and redemption-order management are reachable from the console nav
+
+### Requirement: Shared design system in the platform console
+The platform admin console SHALL use `@vmall/ui` primitives and `@vmall/shared` theme tokens for chrome (buttons, fields, cards, tables, page headers, nav). It MUST NOT depend on Element Plus or the removed `ui.css` stylesheet.
+
+#### Scenario: console chrome from the kit
+- **WHEN** an authenticated platform admin opens the dashboard
+- **THEN** primary actions and page chrome render through the shared kit with the current accent preset
+
+### Requirement: Accent preset switcher
+Platform admin SHALL expose the shared accent preset control (`red`, `blue`, `teal`, `violet`) in the authenticated shell header.
+
+#### Scenario: switcher visible
+- **WHEN** an authenticated platform admin opens the console
+- **THEN** they can select an accent preset without leaving the current page
+