Enhance Hierarchy Population to Support Nodes with Multiple Parents

This commit refines the `populateSelectedNodeHierarchy` method in the `SkillTreeViewModel` to accurately represent nodes that possess multiple parent nodes, ensuring a comprehensive and non-redundant representation of the entire hierarchy leading back to the root nodes.

Modifications and Features:
- The method now employs recursion to traverse all possible paths back to the root nodes from a selected node, capturing every unique node in the hierarchies.
- A `Set` is utilized to monitor and ensure that each node is only added once to the `_selectedNodeHierarchy` list, eliminating the possibility of duplicates.
- The finalized `_selectedNodeHierarchy` list is constructed such that the root of the tree is the last item in the list, providing a more logical representation of the hierarchy.

These enhancements ensure a more accurate and efficient representation of the skill tree structure, particularly in scenarios where nodes have multiple parents, facilitating better navigation and interaction within the skill tree.

frontend/lib/views/task_queue/task_queue_view.dart

@@ -11,9 +11,8 @@ class TaskQueueView extends StatelessWidget {
   Widget build(BuildContext context) {
     final viewModel = Provider.of<SkillTreeViewModel>(context);
 
-    // Reverse the node hierarchy
-    final reversedHierarchy =
-        viewModel.selectedNodeHierarchy?.reversed.toList() ?? [];
+    // Node hierarchy
+    final nodeHierarchy = viewModel.selectedNodeHierarchy ?? [];
 
     return Material(
       color: Colors.white,
@@ -21,9 +20,9 @@ class TaskQueueView extends StatelessWidget {
         children: [
           // The list of tasks (tiles)
           ListView.builder(
-            itemCount: reversedHierarchy.length,
+            itemCount: nodeHierarchy.length,
             itemBuilder: (context, index) {
-              final node = reversedHierarchy[index];
+              final node = nodeHierarchy[index];
 
               // Choose the appropriate leading widget based on the task status
               Widget leadingWidget;