chore: add Claude Code local settings to .gitignore

Added .claude/settings.local.json to .gitignore to prevent user-specific
Claude Code CLI settings from being committed to version control.

These settings contain local paths and session-specific permissions that
are unique to each developer's environment.

.gitignore

@@ -11,4 +11,6 @@ working.png
 ruby/.rails5-gems
 web/.rails5-gems
 websocket-gateway/.rails5-gems
-.pg_data/
+.pg_data/
+# Claude Code local settings
+.claude/settings.local.json