Adopt C# 12 collection expressions for empty lists/dicts

Refactored code to use C# 12 collection expressions ([]) for initializing empty lists and dictionaries instead of the older constructors. This change modernizes and simplifies collection initialization across models, services, and API clients without altering any logic.

DbFirst.BlazorWebApp/Services/BandLayoutService.cs

@@ -88,9 +88,9 @@ namespace DbFirst.BlazorWebApp.Services
             Dictionary<string, ColumnDefinition> columnLookup)
         {
             layout ??= new BandLayout();
-            layout.Bands ??= new List<BandDefinition>();
-            layout.ColumnOrder ??= new List<string>();
-            layout.ColumnWidths ??= new Dictionary<string, string?>(StringComparer.OrdinalIgnoreCase);
+            layout.Bands ??= [];
+            layout.ColumnOrder ??= [];
+            layout.ColumnWidths ??= [];
 
             foreach (var band in layout.Bands)
             {