fix: Resolve frontend API connection issues in Docker

- Add setupProxy.js to proxy API calls to backend container
- Install http-proxy-middleware for development proxy support
- Update docker-compose.dev.yml to use backend service name
- Add HOST=0.0.0.0 to allow external connections to dev server
- Add empty favicon.ico to prevent 500 errors
- Update proxy configuration to use port 7510

This fixes the ERR_CONNECTION_REFUSED errors when the frontend
tries to connect to the backend API in Docker environment.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

docker-compose.dev.yml

@@ -41,7 +41,8 @@ services:
     restart: unless-stopped
     environment:
       PORT: 7511
-      REACT_APP_API_URL: http://localhost:7510/api
+      BACKEND_URL: http://backend:7510
+      DANGEROUSLY_DISABLE_HOST_CHECK: 'true'
     ports:
       - "7511:7511"
     volumes: