refactor(task-list): enhance task row components with depth handling

- Added depth and maxDepth props to TaskRow, TaskRowWithSubtasks, and TitleColumn components to manage nested subtasks more effectively.
- Updated AddSubtaskRow to support depth for proper indentation and visual hierarchy.
- Improved styling for subtasks based on their depth level, ensuring better visual distinction.
- Adjusted task management slice to utilize actual subtask counts from the backend for accurate display.

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

@@ -24,6 +24,7 @@ interface TaskRowProps {
   isSubtask?: boolean;
   isFirstInGroup?: boolean;
   updateTaskCustomColumnValue?: (taskId: string, columnKey: string, value: string) => void;
+  depth?: number;
 }
 
 const TaskRow: React.FC<TaskRowProps> = memo(({ 
@@ -32,7 +33,8 @@ const TaskRow: React.FC<TaskRowProps> = memo(({
   visibleColumns, 
   isSubtask = false, 
   isFirstInGroup = false, 
-  updateTaskCustomColumnValue 
+  updateTaskCustomColumnValue,
+  depth = 0
 }) => {
   // Get task data and selection state from Redux
   const task = useAppSelector(state => selectTaskById(state, taskId));
@@ -107,6 +109,7 @@ const TaskRow: React.FC<TaskRowProps> = memo(({
     handleTaskNameEdit,
     attributes,
     listeners,
+    depth,
   });
 
   // Memoize style object to prevent unnecessary re-renders