fix(admin): make the role-grants page interactive

The role-grants page is the authoring surface for LdapGroupRoleMapping
rows, but it had no @rendermode — so it rendered as static SSR and its
@onclick handlers (Add grant, Revoke) never fired. App.razor's <Routes/>
sets no global render mode; only ClusterDetail opted in.

- Add @rendermode RenderMode.InteractiveServer.
- Fix the SignalR hub URL: the page connected to /hubs/fleet-status,
  but FleetStatusHub is mapped at /hubs/fleet. Static SSR masked this
  (OnAfterRenderAsync never ran); enabling interactivity surfaced the
  404 that terminated the circuit.

Verified in-browser: Add grant opens the form, a cluster-scoped grant
saves and lists, Revoke removes it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Server/ZB.MOM.WW.OtOpcUa.Admin/Components/Pages/RoleGrants.razor

@@ -1,5 +1,6 @@
 @page "/role-grants"
 @attribute [Microsoft.AspNetCore.Authorization.Authorize(Policy = "CanPublish")]
+@rendermode RenderMode.InteractiveServer
 @using Microsoft.AspNetCore.Components.Web
 @using Microsoft.AspNetCore.SignalR.Client
 @using ZB.MOM.WW.OtOpcUa.Admin.Hubs
@@ -179,7 +180,7 @@ else
     {
         if (!firstRender || _hub is not null) return;
         _hub = new HubConnectionBuilder()
-            .WithUrl(Nav.ToAbsoluteUri("/hubs/fleet-status"))
+            .WithUrl(Nav.ToAbsoluteUri("/hubs/fleet"))
             .WithAutomaticReconnect()
             .Build();
         _hub.On<RoleGrantsChangedMessage>("RoleGrantsChanged", async _ =>