refactor(models): add required keyword and remove unused imports

- Add required keyword to string properties across all model classes
- Initialize Part.NestedOn array with Array.Empty<int>()
- Remove unused using statements from model files

This improves null safety and code maintainability.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

PepApi.Core/Models/Material.cs

@@ -4,10 +4,10 @@ namespace PepApi.Core.Models
     {
         public int Number { get; set; }
 
-        public string Grade { get; set; }
+        public required string Grade { get; set; }
 
         public double Thickness { get; set; }
 
-        public string Description { get; set; }
+        public required string Description { get; set; }
     }
 }

PepApi.Core/Models/NestDetails.cs

@@ -1,6 +1,3 @@
-using System;
-using System.Collections.Generic;
-
 namespace PepApi.Core.Models
 {
     public class NestDetails
@@ -11,29 +8,29 @@ namespace PepApi.Core.Models
             Plates = new List<Plate>();
         }
 
-        public string Name { get; set; }
+        public required string Name { get; set; }
 
         public DateTime DateCreated { get; set; }
 
         public DateTime DateLastModified { get; set; }
 
-        public string Status { get; set; }
+        public required string Status { get; set; }
 
-        public string Comments { get; set; }
+        public required string Comments { get; set; }
 
-        public string Customer { get; set; }
+        public required string Customer { get; set; }
 
-        public string ProgrammedBy { get; set; }
+        public required string ProgrammedBy { get; set; }
 
-        public Material Material { get; set; }
+        public required Material Material { get; set; }
 
-        public string Notes { get; set; }
+        public required string Notes { get; set; }
 
         public bool HasErrors { get; set; }
 
-        public string Revision { get; set; }
+        public required string Revision { get; set; }
 
-        public string Application { get; set; }
+        public required string Application { get; set; }
 
         public int NumberOfTestSquares { get; set; }
 

PepApi.Core/Models/NestFilterData.cs

@@ -1,8 +1,3 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using PepLib;
-
 namespace PepApi.Core.Models
 {
     public class NestFilterData

PepApi.Core/Models/NestSummary.cs

@@ -1,35 +1,32 @@
-using PepLib;
-using System;
-
 namespace PepApi.Core.Models
 {
     public class NestSummary
     {
-        public string Name { get; set; }
+        public required string Name { get; set; }
 
         public DateTime DateCreated { get; set; }
 
         public DateTime DateLastModified { get; set; }
 
-        public string Status { get; set; }
+        public required string Status { get; set; }
 
-        public string Comments { get; set; }
+        public required string Comments { get; set; }
 
-        public string Customer { get; set; }
+        public required string Customer { get; set; }
 
-        public string ProgrammedBy { get; set; }
+        public required string ProgrammedBy { get; set; }
 
         public int MaterialNumber { get; set; }
 
-        public string MaterialGrade { get; set; }
+        public required string MaterialGrade { get; set; }
 
-        public string Notes { get; set; }
+        public required string Notes { get; set; }
 
         public bool HasErrors { get; set; }
 
-        public string Revision { get; set; }
+        public required string Revision { get; set; }
 
-        public string Application { get; set; }
+        public required string Application { get; set; }
 
     }
 }

PepApi.Core/Models/Part.cs

@@ -2,9 +2,9 @@ namespace PepApi.Core.Models
 {
     public class Part
     {
-        public string Name { get; set; }
+        public required string Name { get; set; }
         public int QtyNested { get; set; }
         public int QtyRequired { get; set; }
-        public int[] NestedOn { get; set; }
+        public int[] NestedOn { get; set; } = Array.Empty<int>();
     }
 }

PepApi.Core/Models/Plate.cs

@@ -2,13 +2,13 @@ namespace PepApi.Core.Models
 {
     public class Plate
     {
-        public string Name { get; set; }
+        public required string Name { get; set; }
 
         public double Thickness { get; set; }
 
-        public Material Material { get; set; }
+        public required Material Material { get; set; }
 
-        public Size Size { get; set; }
+        public required Size Size { get; set; }
 
         public int Qty { get; set; }