Context\nThe ISSUE-55 branch includes backend UEX orbit entities, migrations, and location sync adjustments that are out of scope for inventory add.\n\n## Scope\n- Add UEX orbit entity/model and relations.\n- Update UEX locations sync to ingest orbit data and link to locations.\n- Update location population to account for new orbit hierarchy.\n- Document UEX location/orbit sync behavior.\n\n## Definition of Done\n- Orbits table + relations are represented in migrations and entities.\n- Location sync pulls orbit data and persists expected relations.\n- Location population uses orbit info where applicable.\n- Docs added/updated for location/orbit sync workflow.\n- Tests updated/added where needed.
