refactor(task-list): simplify drag-and-drop functionality and enhance task rendering

- Removed droppable functionality from TaskGroupHeader and replaced it with a more streamlined approach in TaskListV2Table.
- Introduced DropSpacer component to improve visual feedback during task dragging.
- Updated task rendering logic in TaskRow to enhance user experience with clearer drop indicators.
- Refactored useDragAndDrop hook to manage drop positions more effectively, ensuring tasks can only be reordered within the same group.
- Improved socket event handling for task sorting to ensure accurate updates during drag-and-drop operations.

worklenz-frontend/src/features/task-management/task-management.slice.ts

@@ -680,8 +680,23 @@ const taskManagementSlice = createSlice({
         const group = state.groups.find(g => g.id === sourceGroupId);
         if (group) {
           const newTasks = Array.from(group.taskIds);
-          const [removed] = newTasks.splice(newTasks.indexOf(sourceTaskId), 1);
-          newTasks.splice(newTasks.indexOf(destinationTaskId), 0, removed);
+          const sourceIndex = newTasks.indexOf(sourceTaskId);
+          const destinationIndex = newTasks.indexOf(destinationTaskId);
+          
+          // Remove the task from its current position
+          const [removed] = newTasks.splice(sourceIndex, 1);
+          
+          // Calculate the insertion index
+          let insertIndex = destinationIndex;
+          if (sourceIndex < destinationIndex) {
+            // When dragging down, we need to insert after the destination
+            insertIndex = destinationIndex;
+          } else {
+            // When dragging up, we insert before the destination
+            insertIndex = destinationIndex;
+          }
+          
+          newTasks.splice(insertIndex, 0, removed);
           group.taskIds = newTasks;
 
           // Update order for affected tasks using the appropriate sort field