Add Polaris frontend: storefront + admin console (React 18/Vite/TS/Tailwind)

- Shared src/lib/api.ts fetch wrapper -> /api with Cache-Control: no-store
- Storefront: home hero, shop grid (category filter + search), product detail,
  cart, checkout (POST /api/orders -> confirmation + order number), order tracking
- Admin: JWT login, today KPI dashboard (revenue/orders/gross/net/margin/aov/refunds),
  top products, supplier performance, product import, lifecycle view, order list
  with tracking simulation
- Multi-stage Dockerfile (Vite build -> nginx static + /api proxy -> api:8000)
- nginx.conf with SPA fallback and no-store HTML caching
- mock/mock_api.py for local verification (excluded from image)

frontend/README.md

@@ -0,0 +1,37 @@
+# Polaris — Frontend
+
+React 18 + Vite + TypeScript + Tailwind. Two surfaces sharing one API client (`src/lib/api.ts`):
+
+- **Storefront** `/` — home hero, shop grid (category filter + search), product detail, cart, checkout, order tracking.
+- **Admin** `/admin` — JWT login, today KPI dashboard, top products, supplier performance, product import, lifecycle view, order list with tracking simulation.
+
+## Layout
+
+```
+src/lib/api.ts        shared fetch wrapper → /api, Cache-Control: no-store
+src/lib/types.ts      models mirroring db/schema.sql
+src/store/cart.tsx    cart context (localStorage-persisted)
+src/pages/*           storefront pages
+src/admin/*           admin console pages
+nginx.conf            static + proxy /api → api:8000 (compose service `api`)
+Dockerfile            multi-stage: node build → nginx runtime
+mock/mock_api.py      standalone mock API for local verification (not shipped in image)
+```
+
+## Dev
+
+```bash
+npm install
+npm run dev          # Vite dev server proxies /api → http://localhost:8000
+```
+
+Run the mock API in another terminal: `python3 mock/mock_api.py` (admin: `admin@polaris.shop` / `polaris-admin`).
+
+## Build / verify
+
+```bash
+npm run build        # tsc --noEmit (no TS errors required) + vite build → dist/
+docker build -t polaris-frontend .
+```
+
+The nginx image serves `dist/` and proxies `/api/` to the `api` service on port 8000.