FL-1507 Keep tags without a display name (raw tag fallback)

Jira: https://freedomgroupinternational.atlassian.net/browse/FL-1507 (follow-up to FL-1508). mapTags dropped any tag whose tag_display was empty, so a COMMISSION tag sent without a display name was lost. Now falls back to the raw tag (e.g. COMISSION); tags with neither are still skipped. Consumers may see either the display name or the raw code, so a COMMISSION filter should match both. After merge: tag v1.9.3 and bump etl !42. 🤖 Generated with Claude Code

Closes FL-1507