chore: ignore .ipynb to keep demo/scratch notebooks out of the repo

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: claude

.gitignore

@@ -4,4 +4,7 @@ dist
 abstract_python_ip_geolocation.egg-info
 dev_test.py
 .vscode
-*.history
+*.history
+# Demo / scratch notebooks must not be committed.
+*.ipynb
+.ipynb_checkpoints/