Add API proxy endpoint so users can access running tool instances
through the backend API instead of internal Docker network.
Backend:
- Add container_name field to ToolInstance model
- Create /instances/{id}/proxy/{path:path} endpoint with ownership checks
- Proxy HTTP requests to containers via docker network using container names
- Support all HTTP methods (GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS)
- Store proxy URL in instance.url instead of localhost
- Add Alembic migration 0007 for container_name column
- Add get_container_name() utility to docker.py
Frontend:
- Update Open button to use full proxy URL (API_BASE_URL + instance.url)
Closes instance-proxy OpenSpec change.
Fusion