refactor: update namespaces and improve null handling in view models and controllers

Webzine.WebApplication/Areas/Administration/ViewModels/Styles/StyleDeleteViewModel.cs

@@ -2,7 +2,7 @@
 // Copyright (c) Equipe 1 - BOBIN, MASI, NODON, VETU. All rights reserved.
 // </copyright>
 
-namespace Webzine.WebApplication.Areas.Administration.ViewModels.Style
+namespace Webzine.WebApplication.Areas.Administration.ViewModels.Styles
 {
     /// <summary>
     /// ViewModel pour la suppression d'un style en administration.
@@ -17,6 +17,6 @@ namespace Webzine.WebApplication.Areas.Administration.ViewModels.Style
         /// <summary>
         /// Obtient ou définit le libellé du style.
         /// </summary>
-        public string Libelle { get; set; }
+        public string? Libelle { get; set; }
     }
 }