refactor(PepLib.Core): reorganize files into logical folder structure

Move 38 files from root directory into organized subfolders:
- Enums/ (7 files): StatusType, ApplicationType, DrawingType, etc.
- Geometry/ (5 files): Vector, Box, Size, Spacing, Node
- Models/ (15 files): Nest, Plate, Part, Program, Report, etc.
- Utilities/ (7 files): MathHelper, Tolerance, ZipHelper, etc.
- Extensions/ (2 files): PartListExtensions, PlateListExtensions
- Interfaces/ (1 file): IMovable

Update namespaces to follow folder hierarchy (e.g., PepLib.Models).
Add GlobalUsings.cs for internal backward compatibility.
Update Codes/ and IO/ files with new using statements.
Update PepApi.Core consumers to reference new namespaces.

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

PepLib.Core/Utilities/Util.cs

@@ -0,0 +1,30 @@
+using System.Diagnostics;
+
+namespace PepLib.Utilities
+{
+    public static class Util
+    {
+        public static string GetNestFileFormat(string filename)
+        {
+            try
+            {
+                var name = Path.GetFileName(filename);
+                var ext = Path.GetExtension(name);
+
+                if (name.LastIndexOf(ext) > 5 && !name.Contains("-"))
+                    name = name.Insert(5, "-");
+
+                if (name.LastIndexOf(ext) > 8 && char.IsLetter(name[8]))
+                    name = name.Remove(8, 1);
+
+                return Path.Combine(Path.GetDirectoryName(filename), name);
+            }
+            catch (SystemException ex)
+            {
+                Debug.WriteLine(ex.Message);
+            }
+
+            return string.Empty;
+        }
+    }
+}