Bump onnx minimum version to fix path traversal vulnerability (CVE)

onnx 1.17.0 is vulnerable to path traversal via symlink. Updating
the pin to >=1.18.0 resolves the GitHub security alert.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jkgoodrich

requirements.txt

@@ -4,7 +4,7 @@ hail
 hdbscan
 ipywidgets
 networkx
-onnx==1.17.0
+onnx>=1.18.0
 onnxruntime
 scikit-learn
 skl2onnx