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/Extensions/PartListExtensions.cs

@@ -0,0 +1,40 @@
+using PepLib.Geometry;
+using PepLib.Models;
+
+namespace PepLib.Extensions
+{
+    public static class PartListExtensions
+    {
+        public static Box GetBoundingBox(this List<Part> parts)
+        {
+            if (parts.Count == 0)
+                return new Box();
+
+            var firstpart = parts[0];
+
+            double minX = firstpart.BoundingBox.X;
+            double minY = firstpart.BoundingBox.Y;
+            double maxX = firstpart.BoundingBox.X + firstpart.BoundingBox.Width;
+            double maxY = firstpart.BoundingBox.Y + firstpart.BoundingBox.Height;
+
+            foreach (var part in parts)
+            {
+                var box = part.BoundingBox;
+
+                if (box.Left < minX)
+                    minX = box.Left;
+
+                if (box.Right > maxX)
+                    maxX = box.Right;
+
+                if (box.Bottom < minY)
+                    minY = box.Bottom;
+
+                if (box.Top > maxY)
+                    maxY = box.Top;
+            }
+
+            return new Box(minX, minY, maxX - minX, maxY - minY);
+        }
+    }
+}

PepLib.Core/Extensions/PlateListExtensions.cs

@@ -0,0 +1,41 @@
+using PepLib.Models;
+
+namespace PepLib.Extensions
+{
+    public static class PlateListExtensions
+    {
+        public static void JoinLikePlates(this List<Report.Plate> plates)
+        {
+        START:
+
+            for (int i = 0; i < plates.Count; ++i)
+            {
+                var p1 = plates[i];
+
+                for (int j = 0; j < plates.Count; ++j)
+                {
+                    var p2 = plates[j];
+
+                    if (i == j)
+                        continue;
+
+                    if (p1.Width != p2.Width)
+                        continue;
+
+                    if (p1.Length != p2.Length)
+                        continue;
+
+                    if (p1.MaterialDescription != p2.MaterialDescription)
+                        continue;
+
+                    if (p1.Thickness != p2.Thickness)
+                        continue;
+
+                    p1.Quantity += p2.Quantity;
+                    plates.Remove(p2);
+                    goto START;
+                }
+            }
+        }
+    }
+}