Add dd0c/route Dashboard UI: React + Vite + Tailwind SPA

- Layout with sidebar navigation (Dashboard, Rules, Keys, Settings)
- Dashboard page: stat cards, cost savings area chart (Recharts), model usage table
- Rules page: routing rules CRUD with modal editor, strategy/complexity/model matching
- Keys page: API key generation, copy-once reveal, revocation, quick-start code snippet
- Settings page: org info, provider config, danger zone
- API client (SWR + fetch wrapper) with full TypeScript types
- dd0c dark theme: indigo primary, cyan accent, dark surfaces
- Vite proxy config for local dev against API on :3000

products/01-llm-cost-router/ui/tailwind.config.js

@@ -0,0 +1,23 @@
+/** @type {import('tailwindcss').Config} */
+export default {
+  content: ['./index.html', './src/**/*.{js,ts,jsx,tsx}'],
+  theme: {
+    extend: {
+      colors: {
+        dd0c: {
+          bg: '#0a0a0f',
+          surface: '#12121a',
+          border: '#1e1e2e',
+          primary: '#6366f1',
+          accent: '#06b6d4',
+          success: '#22c55e',
+          warning: '#f59e0b',
+          danger: '#ef4444',
+          text: '#e2e8f0',
+          muted: '#64748b',
+        },
+      },
+    },
+  },
+  plugins: [],
+};