Add the ability to deselect a task

frontend/lib/viewmodels/task_viewmodel.dart

@@ -73,4 +73,11 @@ class TaskViewModel with ChangeNotifier {
       throw ArgumentError(errorMessage);
     }
   }
+
+  /// Deselects the currently selected task.
+  void deselectTask() {
+    _selectedTask = null;
+    print("Deselected the current task.");
+    notifyListeners(); // Notify listeners to rebuild UI
+  }
 }

frontend/lib/views/task/task_view.dart

@@ -46,6 +46,7 @@ class _TaskViewState extends State<TaskView> {
                   final chatViewModel =
                       Provider.of<ChatViewModel>(context, listen: false);
                   chatViewModel.clearCurrentTaskAndChats();
+                  widget.viewModel.deselectTask();
                   print(
                       'New Task button pressed, cleared current task ID and chats');
                 },