feat(AssigneeSelector): add kanbanMode prop for enhanced task assignment

- Introduced kanbanMode prop to AssigneeSelector and LazyAssigneeSelectorWrapper for improved functionality in Kanban view.
- Updated EnhancedKanbanTaskCard and TaskCard components to utilize the new kanbanMode prop.
- Adjusted task sorting logic to handle cases where sort_order may be undefined, ensuring robust behavior during task updates.

worklenz-frontend/src/components/enhanced-kanban/EnhancedKanbanBoardNativeDnD/TaskCard.tsx

@@ -381,7 +381,7 @@ const TaskCard: React.FC<TaskCardProps> = memo(({
                                     isDarkMode={themeMode === 'dark'}
                                     size={24}
                                 />
-                                <LazyAssigneeSelectorWrapper task={task} groupId={groupId} isDarkMode={themeMode === 'dark'} />
+                                <LazyAssigneeSelectorWrapper task={task} groupId={groupId} isDarkMode={themeMode === 'dark'} kanbanMode={true} />
                                 {(task.sub_tasks_count ?? 0) > 0 && (
                                     <button
                                         type="button"