Split 1200+ line file into clean modular architecture:
- FocusAreaNode.jsx - Tree nodes with nested style directions + training types
- HierarchyTab.jsx - Tab 1 with tree view and detail panel
- CatalogsTab.jsx - Tab 2 with global catalogs (Target Groups, Skill Categories, Training Characters)
- AssignmentsTab.jsx - Tab 3 with M:N checkbox matrix (Style Directions ↔ Target Groups)
- DetailPanel.jsx - All edit forms (Focus Area, Style Direction, Training Type) + create forms
Fixes ESBuild parser error from large file size.
Implements full CRUD: create, edit, delete, reassign focus areas.
Responsive design with mobile/desktop layouts.
