Marimo's Files panel showed 'no storage connected' because obstore
and s3fs weren't installed in the notebooks container.
- Add obstore + s3fs to notebooks/Dockerfile
- Add obstore + s3fs as dev deps in pyproject.toml
- Add connect.obstore() factory — returns S3Store auto-configured
from env vars, which marimo auto-discovers in Files → Remote Storage
- Update _template.py: new notebooks come with S3 pre-connected
- Add obstore snippet to connections.py
- 2 new tests, 100% coverage maintained
fix#81
b6f21f497c
