feat(data): add nullable max_turns override to list_config and tasks

src/ClaudeDo.Data/Models/ListConfigEntity.cs

@@ -6,6 +6,7 @@ public sealed class ListConfigEntity
     public string? Model { get; set; }
     public string? SystemPrompt { get; set; }
     public string? AgentPath { get; set; }
+    public int? MaxTurns { get; set; }
 
     // Navigation property
     public ListEntity List { get; set; } = null!;