Fix NestFilterData properties to be nullable for optional filtering

- Make all string properties nullable (Name, Customer, Comments, etc.)
- Fixes "all fields are required" error in Swagger UI and API validation
- Filter properties are optional query parameters, not required fields

All filter logic already checks for null values before applying filters,
so this change aligns the model definition with its actual usage.

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

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

PepApi.Core/Models/NestFilterData.cs

@@ -7,11 +7,11 @@ namespace PepApi.Core.Models
 {
     public class NestFilterData
     {
-        public string Name { get; set; }
+        public string? Name { get; set; }
 
-        public string Customer { get; set; }
+        public string? Customer { get; set; }
 
-        public string Comments {get;set;}
+        public string? Comments { get; set; }
 
         public DateTime? StartDate { get; set; }
 
@@ -19,15 +19,15 @@ namespace PepApi.Core.Models
 
         public int? MaterialNumber { get; set; }
 
-        public string MaterialGrade { get; set; }
+        public string? MaterialGrade { get; set; }
 
-        public string ProgrammedBy { get; set; }
+        public string? ProgrammedBy { get; set; }
 
-        public string Notes { get; set; }
+        public string? Notes { get; set; }
 
-        public string Status { get; set; }
+        public string? Status { get; set; }
 
-        public string Application { get; set; }
+        public string? Application { get; set; }
 
         public IQueryable<NestSummary> Apply(IQueryable<NestSummary> nests)
         {