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)
             {

DbFirst.BlazorWebApp/Services/CatalogApiClient.cs

@@ -17,7 +17,7 @@ public class CatalogApiClient : ICatalogApiClient
     public async Task<List<CatalogReadDto>> GetAllAsync(CancellationToken ct = default)
     {
         var result = await _httpClient.GetFromJsonAsync<List<CatalogReadDto>>(Endpoint, ct);
-        return result ?? new List<CatalogReadDto>();
+        return result ?? [];
     }
 
     public async Task<CatalogReadDto?> GetByIdAsync(int id, CancellationToken ct = default)

DbFirst.BlazorWebApp/Services/DashboardApiClient.cs

@@ -16,6 +16,6 @@ public class DashboardApiClient : IDashboardApiClient
     public async Task<List<DashboardInfoDto>> GetAllAsync(CancellationToken ct = default)
     {
         var result = await _httpClient.GetFromJsonAsync<List<DashboardInfoDto>>(Endpoint, ct);
-        return result ?? new List<DashboardInfoDto>();
+        return result ?? [];
     }
 }

DbFirst.BlazorWebApp/Services/MassDataApiClient.cs

@@ -33,7 +33,7 @@ public class MassDataApiClient : IMassDataApiClient
 
         var url = query.Count == 0 ? Endpoint : $"{Endpoint}?{string.Join("&", query)}";
         var result = await _httpClient.GetFromJsonAsync<List<MassDataReadDto>>(url, ct);
-        return result ?? new List<MassDataReadDto>();
+        return result ?? [];
     }
 
     public async Task<ApiResult<MassDataReadDto?>> UpsertAsync(MassDataWriteDto dto, CancellationToken ct = default)