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/Geometry/Node.cs

@@ -0,0 +1,82 @@
+namespace PepLib.Geometry
+{
+    public class Node
+    {
+        private Node parent;
+
+        public List<Node> Children;
+
+        public Node()
+        {
+            Children = new List<Node>();
+        }
+
+        public Node Parent
+        {
+            get { return parent; }
+            set
+            {
+                parent = value;
+                UpdateDepth();
+            }
+        }
+
+        public string Value { get; set; }
+
+        private void UpdateDepth()
+        {
+            if (Parent != null)
+                Level = Parent.Level + 1;
+            else
+                Level = 0;
+
+            foreach (var node in Children)
+                node.Parent = this;
+        }
+
+        public int Level { get; protected set; }
+
+        public void AddChild(Node node)
+        {
+            node.Parent = this;
+            Children.Add(node);
+        }
+
+        public void Write(TextWriter writer)
+        {
+            writer.WriteLine("".PadLeft(Level * 2) + this.ToString());
+
+            foreach (var node in Children)
+                node.Write(writer);
+        }
+
+        public override string ToString()
+        {
+            return Value;
+        }
+    }
+
+    public class KeyNode : Node
+    {
+        public string Name;
+
+        public static KeyNode Parse(Node node)
+        {
+            var index = node.Value.IndexOf('=');
+
+            if (index == -1)
+                return null;
+
+            return new KeyNode()
+            {
+                Name = node.Value.Remove(index),
+                Value = node.Value.Remove(0, index + 1).Trim()
+            };
+        }
+
+        public override string ToString()
+        {
+            return string.Format("{0}={1}", Name, Value);
+        }
+    }
+}