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/vite.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from 'vite';
+import react from '@vitejs/plugin-react';
+
+export default defineConfig({
+  plugins: [react()],
+  server: {
+    port: 5173,
+    proxy: {
+      '/api': 'http://localhost:3000',
+    },
+  },
+  build: {
+    outDir: 'dist',
+  },
+});