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/Models/Part.cs

@@ -0,0 +1,127 @@
+using PepLib.Enums;
+using PepLib.Geometry;
+using PepLib.Interfaces;
+
+namespace PepLib.Models
+{
+    public class Part : IMovable
+    {
+        private Loop baseLoop;
+        private Vector location;
+
+        private Part()
+        {
+            BoundingBox = new Box();
+        }
+
+        public Box BoundingBox { get; protected set; }
+
+        public Vector Location
+        {
+            get { return location; }
+            set
+            {
+                BoundingBox.Offset(value - location);
+                location = value;
+            }
+        }
+
+        public string Name
+        {
+            get { return baseLoop.Name; }
+            set { baseLoop.Name = value; }
+        }
+
+        /// <summary>
+        /// Reference point relative to the part location.
+        /// </summary>
+        public Vector ReferencePoint
+        {
+            get { return baseLoop.ReferencePoint; }
+            set { baseLoop.ReferencePoint = value; }
+        }
+
+        /// <summary>
+        /// Reference point relative to the zero point.
+        /// </summary>
+        public Vector AbsoluteReferencePoint
+        {
+            get { return baseLoop.ReferencePoint + location; }
+            set { baseLoop.ReferencePoint = value - location; }
+        }
+
+        public DateTime LastReferenceDate
+        {
+            get { return baseLoop.LastReferenceDate; }
+            set { baseLoop.LastReferenceDate = value; }
+        }
+
+        public string DrawingName
+        {
+            get { return baseLoop.DrawingName; }
+            set { baseLoop.DrawingName = value; }
+        }
+
+        public string DxfPath
+        {
+            get { return baseLoop.DxfPath; }
+            set { baseLoop.DxfPath = value; }
+        }
+
+        public double Rotation
+        {
+            get { return baseLoop.Rotation; }
+        }
+
+        public bool IsDisplayOnly { get; set; } = false;
+
+        public void Rotate(double angle)
+        {
+            baseLoop.Rotate(angle);
+            location = Location.Rotate(angle);
+            UpdateBounds();
+        }
+
+        public void Rotate(double angle, Vector origin)
+        {
+            baseLoop.Rotate(angle);
+            location = Location.Rotate(angle, origin);
+            UpdateBounds();
+        }
+
+        public void Offset(double x, double y)
+        {
+            location = new Vector(location.X + x, location.Y + y);
+            BoundingBox.Offset(x, y);
+        }
+
+        public void Offset(Vector voffset)
+        {
+            location += voffset;
+            BoundingBox.Offset(voffset);
+        }
+
+        public Program Program
+        {
+            get { return baseLoop; }
+        }
+
+        public void UpdateBounds()
+        {
+            BoundingBox = baseLoop.GetBoundingBox();
+            BoundingBox.Offset(Location);
+        }
+
+        public static Part Create(Loop loop, Vector location, double rotation = 0.0)
+        {
+            var part = new Part();
+            part.baseLoop = (Loop)loop.Clone();
+            part.baseLoop.Mode = ProgrammingMode.Incremental;
+            part.baseLoop.Rotate(rotation);
+            part.Location = location;
+            part.UpdateBounds();
+
+            return part;
+        }
+    }
+}