Organization hierarchy

Build the org's tree: mandatory Head Office at the top, then any depth below — Zone, Division, Area, Branch, Team, or custom unit types.

• Visual tree view with expand/collapse + drag-and-drop reorganization
• Unit types editor (rename, add custom types, control children rules)
• Departments (cross-cutting, can span multiple units)
• Teams (under units, with optional team lead)
• Geofence per unit for attendance
• Hierarchy access rules — who can create what at which level

Full spec: docs/modules/hierarchy/BLUEPRINT.md