Add hot reload for frontend and backend

Why

Right now every code change requires rebuilding the containers. Mounting the source directories into the containers means edits show up in the browser immediately, which you'll want dozens of times a day.

Files to touch

• docker-compose.yml
• backend/Dockerfile (or the api service command)

Definition of done

• ./backend is bind-mounted into the api container
• ./frontend is bind-mounted into the web container (excluding node_modules)
• uvicorn runs with --reload
• Editing main.py or App.jsx shows up in the browser without restarting compose

Hints

Look at the volumes: key on a service. For the frontend, mount an anonymous volume over node_modules so the host copy doesn't shadow the container's.

Start in docker-compose.yml by inspecting the api and web services and their existing volumes and commands; check backend/Dockerfile if the api command is defined there. Add the requested source mounts, preserve the frontend node_modules volume, and enable uvicorn reload. Verify by editing backend/main.py and frontend/App.jsx while compose is running and confirming the browser updates without a restart.