feat(task-list): refine task list components and improve UI consistency

- Updated SubtaskLoadingSkeleton and TaskRow components for better spacing and visual consistency.
- Simplified TaskGroupHeader by removing unnecessary elements and enhancing the display of group names.
- Adjusted TaskListV2 to improve column rendering and added state management for field visibility synchronization with the database.
- Enhanced AddTaskRow and AddSubtaskRow components for improved user interaction and layout.
- Updated placeholder texts in CustomColumnComponents for better clarity.

worklenz-frontend/src/components/task-list-v2/TaskRow.tsx

@@ -261,7 +261,7 @@ const TaskRow: React.FC<TaskRowProps> = memo(({ taskId, projectId, visibleColumn
       case 'dragHandle':
         return (
           <div
-            className={`flex items-center justify-center ${isSubtask ? '' : 'cursor-grab active:cursor-grabbing'}`}
+            className="flex items-center justify-center"
             style={baseStyle}
             {...(isSubtask ? {} : { ...attributes, ...listeners })}
           >