fix: re-add drawings to list when parts are deleted with hide-depleted active

The timer-based list update only removed depleted drawings but never
added them back when they became un-depleted (e.g., after deleting a
part from the plate).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest/Forms/EditNestForm.cs

@@ -955,6 +955,15 @@ namespace OpenNest.Forms
                             drawingListBox1.Items.RemoveAt(i);
                     }
 
+                    foreach (var dwg in Nest.Drawings.OrderBy(d => d.Name))
+                    {
+                        if (dwg.Quantity.Required > 0 && dwg.Quantity.Remaining == 0)
+                            continue;
+
+                        if (!drawingListBox1.Items.Contains(dwg))
+                            drawingListBox1.Items.Add(dwg);
+                    }
+
                     drawingListBox1.EndUpdate();
                 }