fix: add API proxy to Vite dev server for web mode CORS

When running in web mode (npm run dev:web), the frontend on localhost:3007
was making cross-origin requests to the backend on localhost:3008, causing
CORS errors.

Added Vite proxy configuration to forward /api requests from the dev server
to the backend. This makes all API calls appear same-origin to the browser,
eliminating CORS blocks during development.

Now web mode users can access http://localhost:3007 without CORS errors.

Fixes: CORS "Not allowed by CORS" errors in web mode

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

apps/ui/vite.config.mts

@@ -68,6 +68,12 @@ export default defineConfig(({ command }) => {
       host: process.env.HOST || '0.0.0.0',
       port: parseInt(process.env.TEST_PORT || '3007', 10),
       allowedHosts: true,
+      proxy: {
+        '/api': {
+          target: 'http://localhost:3008',
+          changeOrigin: true,
+        },
+      },
     },
     build: {
       outDir: 'dist',