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/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)