fix(test): give Ui.Tests task seeds a unique Number

The task-numbers slice added a UNIQUE index on tasks.number. Ui.Tests seed
TaskEntity rows directly instead of going through TaskRepository, so every row
kept the default Number = 0 and 31 tests failed with
'UNIQUE constraint failed: tasks.number'.

tests/ClaudeDo.Ui.Tests/ViewModels/TasksIslandRemoveFromQueueTests.cs

@@ -56,6 +56,7 @@ public class TasksIslandRemoveFromQueueTests : IDisposable
         });
         db.Tasks.Add(new TaskEntity
         {
+            Number = TestTaskNumbers.Next(),
             Id = parentId,
             ListId = "list1",
             Title = "Parent",
@@ -69,6 +70,7 @@ public class TasksIslandRemoveFromQueueTests : IDisposable
             var c = children[i];
             db.Tasks.Add(new TaskEntity
             {
+                Number = TestTaskNumbers.Next(),
                 Id = c.Id,
                 ListId = "list1",
                 Title = $"Child {i}",
@@ -143,6 +145,7 @@ public class TasksIslandRemoveFromQueueTests : IDisposable
             });
             db.Tasks.Add(new TaskEntity
             {
+                Number = TestTaskNumbers.Next(),
                 Id = "solo",
                 ListId = "list1",
                 Title = "Solo",