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/Components/BandGridBase.cs

@@ -162,7 +162,7 @@ public abstract class BandGridBase<TItem> : ComponentBase
 
     protected void UpdateBandOptions()
     {
-        bandOptions = new List<BandOption> { new() { Id = string.Empty, Caption = "Ohne Band" } };
+        bandOptions = [new() { Id = string.Empty, Caption = "Ohne Band" }];
         bandOptions.AddRange(bandLayout.Bands.Select(b => new BandOption { Id = b.Id, Caption = b.Caption }));
     }