Multi-Organization Hierarchy

NHF's organizational structure - 1,400 local chapters - cannot be represented with a flat user model. Without hierarchy support, activities registered under NHF cannot be correctly attributed to the right chapter, region, or national association, making Bufdir reports inaccurate and risking funding compliance. The feature also directly addresses duplicate registration: multiple coordinators across chapters may register the same activity, and hierarchy-aware data structures enable the platform to detect and flag such duplicates before they corrupt reported figures. This is a Phase 1 MUST because incorrect data at MVP launch would undermine trust in the entire platform across all four organizations.

Hierarchy is modeled in the organization_hierarchy_nodes table as an adjacency list with a self-referential parent_id. The admin UI exposes a tree view for managing nodes and assigning users to the correct level. API queries are hierarchy-aware: filtering activities, contacts, and reports by organizational subtree requires recursive CTE queries in Postgres. User membership across multiple local chapters (up to 5 per NHF member) is supported via the user_organization_roles join table with a composite key. Access control rules must respect hierarchy depth - a regional coordinator sees their region's chapters but not others. Circular reference prevention is required in node creation logic.