Add security entries to .gitignore

- Added rules to ignore certificate and key files (*.pem, *.key, *.crt, *.cert, *.p12, *.pfx) to enhance security and prevent accidental commits of sensitive information.

.gitignore

@@ -41,3 +41,11 @@ llm_comparison_*.csv
 llm_config_*.json
 *.log
 
+# Security - Never commit certificates or keys
+*.pem
+*.key
+*.crt
+*.cert
+*.p12
+*.pfx
+