Updated TaskAssigneeList component to accept both UserPublic and TaskAssignee
types, since TaskAssignee doesn't include email field for payload optimization.

The getDisplayName function now:
- Prefers full_name if available
- Falls back to email for UserPublic type
- Shows 'User' for TaskAssignee without full_name

Fixes TypeScript errors in:
- KanbanColumn.tsx
- ProjectTasksKanbanView.tsx
- ProjectTasksTableView.tsx
- SortableTaskRow.tsx