Users reported "Unable to Connect to API Server" errors on startup
because the frontend started before the API finished initialization
(database migrations, etc.).
- Add wait-for-api.sh script that polls /health endpoint
- Update supervisord configs to use wait script instead of sleep 5
- Waits up to 5 minutes for API to be ready before starting frontend
- Applies to both single-container and multi-container deployments
Fixes#315
