Resolve all high-severity architecture review findings

src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Shared/SessionExpiry.razor

@@ -2,28 +2,11 @@
 @inject NavigationManager Navigation
 @inject IJSRuntime JS
 
+<AntiforgeryToken />
+
 @code {
-    // CentralUI-005 / CentralUI-020: session expiry is a sliding window owned by
-    // the cookie authentication middleware (ZB.MOM.WW.ScadaBridge.Security AddCookie:
-    // ExpireTimeSpan = idle timeout, SlidingExpiration = true). An active user's
-    // cookie is continually renewed; an idle user's cookie lapses after the idle
-    // timeout. There is no fixed login-time deadline to redirect at.
-    //
-    // This component must NOT poll the Blazor AuthenticationStateProvider:
-    // CookieAuthenticationStateProvider serves a frozen constructor-time
-    // principal for the whole circuit (CentralUI-004), so the polled auth state
-    // can never transition to "expired" and the redirect would never fire
-    // (CentralUI-020).
-    //
-    // Instead it polls the server endpoint GET /auth/ping via fetch(). Being a
-    // normal HTTP request, the cookie middleware re-validates — and slides — the
-    // cookie on every hit, and answers 200 while the session is live or 401 once
-    // it has lapsed. A genuine idle user's circuit produces no other HTTP
-    // traffic, so once the cookie lapses the next ping returns 401 and this
-    // component redirects to /login. (The ping itself slides the cookie, but the
-    // poll interval is well under the idle timeout, so an idle session still
-    // lapses on schedule once the poll catches the lapsed state — the ping only
-    // ever observes expiry, it does not keep a dead session alive.)
+    // Passive HTTP probes observe expiry but never advance activity. The JS module
+    // separately reports trusted browser input through an antiforgery-protected POST.
 
     /// <summary>Server endpoint that reports live session validity.</summary>
     internal const string PingUrl = "/auth/ping";
@@ -49,6 +32,14 @@
         _ = PollSessionAsync(_cts.Token);
     }
 
+    protected override async Task OnAfterRenderAsync(bool firstRender)
+    {
+        if (!firstRender || IsOnLoginPage) return;
+        try { _module ??= await JS.InvokeAsync<IJSObjectReference>("import", ModulePath); }
+        catch (JSDisconnectedException) { }
+        catch (JSException) { }
+    }
+
     private bool IsOnLoginPage =>
         Navigation.ToBaseRelativePath(Navigation.Uri)
             .StartsWith("login", StringComparison.OrdinalIgnoreCase);