Resolve all high-severity architecture review findings

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/Sites.razor

@@ -1,3 +1,6 @@
+@using ZB.MOM.WW.ScadaBridge.CentralUI.Services
+@using ZB.MOM.WW.ScadaBridge.Commons.Messages.Management
+@inject IServiceProvider MutationServices
 @* Reference pattern for list pages: card grid (col-lg-6) + flex header + search filter + kebab dropdown + Bootstrap collapse for noisy detail + @key on iterated cards + "No X match the filter." inline + empty-state CTA. Mirror this when building new list pages. *@
 @page "/admin/sites"
 @using ZB.MOM.WW.ScadaBridge.Security
@@ -165,7 +168,7 @@
     // CentralUI-024: delegates to the shared helper so the claim type stays
     // resolved through JwtTokenService rather than a duplicated magic string.
     private Task<string> GetCurrentUserAsync()
-        => AuthStateProvider.GetCurrentUsernameAsync();
+        => AuthStateProvider.RequireRoleAsync(ZB.MOM.WW.ScadaBridge.Security.Roles.Administrator);
 
     private List<Site> _sites = new();
     private Dictionary<int, List<DataConnection>> _siteConnections = new();
@@ -221,8 +224,7 @@
 
         try
         {
-            await SiteRepository.DeleteSiteAsync(site.Id);
-            await SiteRepository.SaveChangesAsync();
+            await MutationServices.ExecuteConfigurationAsync(new DeleteSiteCommand(site.Id));
             CommunicationService.RefreshSiteAddresses();
             _toast.ShowSuccess($"Site '{site.Name}' deleted.");
             await LoadDataAsync();