feat(planner/python): Implement streamlit support

[pan93412]

Spec

Discovery behavior

1. Projects with zbpack.json including {"streamlit": {"entry": "<entry>"}}. will be used.
   • requirements.txt is required if there is no any file named app.py, main.py or streamlit_app.py.
2. For app.py, main.py, streamlit_app.py files including import streamlit: such file will be used.

Installation behavior

For all Streamlit projects, we install streamlit automatically even there is no requirements.txt.

Launch behavior

We run it with <pkg-manager-pre-args> streamlit run <entry> --server.port=8080 --server.address=0.0.0.0, while 8080 is Zeabur's default listening port.