v1.9.0

Merge branch 'develop' into main

Brings develop up to date with sync-to-public workflow and v1.9.0 changes:
- ci: automated sync workflow to jpazvd/yaml via staging branch
- test: wbopendata and unicefdata integration tests (26 total)
- docs: paper, README, QA docs aligned with v1.9.0
- chore: .gitignore updated for QA fixtures and LaTeX artifacts