Build dea-scripts (Python catalog automation)

## Task\nPython scripts for catalog automation: sync, convert, validate, generate.

## Definition of Done
- [ ] CSV ↔ SQLite ↔ YAML converter
- [ ] RDFLib TTL validation against dea-metamodel
- [ ] Viewpoint generator (Markdown + PlantUML)
- [ ] Bulk Excel/CSV import to catalog format