chore: clean up .gitignore

Remove duplicate .venv entry, add .claude/ so local dev-server configs
and permission settings are never accidentally committed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -9,3 +9,4 @@ venv/
 *.env
 baseline_scores.json
 .DS_Store
+.claude/