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/tailwind.config.js

@@ -0,0 +1,44 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  content: ['./index.html', './src/**/*.{ts,tsx}'],
+  theme: {
+    extend: {
+      colors: {
+        night: {
+          950: '#03050d',
+          900: '#04060f',
+          800: '#070b18',
+          700: '#0b1126',
+          600: '#111a38',
+          500: '#1a2447',
+        },
+        aurora: {
+          200: '#c7d2fe',
+          300: '#a5b4fc',
+          400: '#818cf8',
+          500: '#6366f1',
+          600: '#4f46e5',
+        },
+      },
+      fontFamily: {
+        sans: [
+          'Inter',
+          'ui-sans-serif',
+          'system-ui',
+          '-apple-system',
+          'Segoe UI',
+          'Roboto',
+          'Helvetica Neue',
+          'Arial',
+          'sans-serif',
+        ],
+        mono: ['ui-monospace', 'SFMono-Regular', 'Menlo', 'Consolas', 'monospace'],
+      },
+      boxShadow: {
+        glass: '0 8px 32px rgba(2, 6, 23, 0.55)',
+        glow: '0 0 40px rgba(99, 102, 241, 0.35)',
+      },
+    },
+  },
+  plugins: [],
+}