Add a new make dev-daemon target that allows running DeerFlow services
in background mode without keeping the terminal connection.
Following the pattern of PR #1042, the implementation uses a dedicated
shell script (scripts/start-daemon.sh) for better maintainability.
- Create scripts/start-daemon.sh for daemon mode startup
- Add dev-daemon target to Makefile
- Each service writes logs to separate files (langgraph, gateway, frontend, nginx)
- Services can be stopped with make stop
- Use nohup for proper daemon process detachment
- Add cleanup on failure when services fail to start
- Use more specific pkill pattern to avoid killing unrelated nginx processes
echoyolo6