Refactor: centralize grid band layout logic in service

Introduce BandLayoutService and shared models to manage grid band layouts across components. Refactor CatalogsGrid and MassDataGrid to use the new service, removing duplicated layout logic. Update _Imports.razor and register the service in Program.cs for improved maintainability and code reuse.

DbFirst.BlazorWebApp/Models/Grid/BandLayoutModels.cs

@@ -0,0 +1,43 @@
+using DevExpress.Blazor;
+
+namespace DbFirst.BlazorWebApp.Models.Grid
+{
+    public class BandLayout
+    {
+        public List<BandDefinition> Bands { get; set; } = new();
+        public List<string> ColumnOrder { get; set; } = new();
+        public Dictionary<string, string?> ColumnWidths { get; set; } = new(StringComparer.OrdinalIgnoreCase);
+        public GridPersistentLayout? GridLayout { get; set; }
+        public SizeMode SizeMode { get; set; } = SizeMode.Medium;
+    }
+
+    public class BandDefinition
+    {
+        public string Id { get; set; } = string.Empty;
+        public string Caption { get; set; } = string.Empty;
+        public List<string> Columns { get; set; } = new();
+    }
+
+    public class BandOption
+    {
+        public string Id { get; set; } = string.Empty;
+        public string Caption { get; set; } = string.Empty;
+    }
+
+    public class ColumnDefinition
+    {
+        public string FieldName { get; init; } = string.Empty;
+        public string Caption { get; init; } = string.Empty;
+        public string? Width { get; set; }
+        public string? DisplayFormat { get; init; }
+        public bool ReadOnly { get; init; }
+        public ColumnFilterType FilterType { get; init; }
+    }
+
+    public enum ColumnFilterType
+    {
+        Text,
+        Bool,
+        Date
+    }
+}