feat(core,io): persist nest status and made-by in nest files

Add NestStatus (Quote/ToBeCut/HasBeenCut) plus MadeBy on Nest, written as
additive camelCase nest.json fields with PascalCase enum strings matching
the units convention. Legacy files and unknown status values fall back to
Quote. The nest info dialog gains a Status dropdown and Made By box.

OpenNest.Core/Nest.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using OpenNest.Collections;
 using OpenNest.Geometry;
@@ -38,6 +38,10 @@ namespace OpenNest
 
         public string AssistGas { get; set; } = "";
 
+        public NestStatus Status { get; set; } = NestStatus.Quote;
+
+        public string MadeBy { get; set; } = "";
+
         public double Thickness { get; set; }
 
         public Material Material { get; set; }