refactor: Update using statements for relocated types

Updates imports across the codebase to reference the new namespaces
for Formatting utilities, Document, BinFileSaver, and Toolbox.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CutList.Core/Bin.cs

@@ -1,6 +1,4 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
+using CutList.Core.Formatting;
 
 namespace CutList.Core
 {