Restore .gitignore, and ignore the CI virtualenv

The file had been deleted in the working tree, which is why __pycache__
started showing up as untracked. .venv-ci is the throwaway environment
the deploy workflow builds inside the runner's checkout.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -142,6 +142,7 @@ __pycache__/
 *.py[cod]
 .venv/
 venv/
+.venv-ci/
 
 # Learned HEOS group membership, written at runtime
 members.json