Back closes what is open

On a phone the Back button left the page under an open menu, sheet or dialog. An open overlay now says so (new
IDOverlayHost, cascaded by MainLayout; OverlayService keeps them newest last): DModal and DDropdown through the
cascade, so the D components stay free of app services, and the nav menu, PhoneSheet and the full-screen globe through
the service. MainLayout's location-changing handler lets Back close the newest overlay instead of leaving the page; a
link followed or the app's own navigation (signing out after its question, say) closes them all and goes on. Blazor
can't tell Back from the app's navigation, so a capture-phase popstate listener in main.js marks Back
(AppStatusService.TookBack). No history entries are pushed. Phone flow: Back closes the menu, a card's More sheet, the
composer and the full-screen globe one after another without leaving the feed, and with nothing open goes back.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

Services/AppStatusService.cs

@@ -42,6 +42,9 @@ public class AppStatusService(IJSRuntime jsRuntime)
 
 		public bool IsMobileMedia() => JsSyncRuntime.Invoke<bool>("isMobileMedia");
 
+		// whether the navigation being decided came from the Back (or Forward) button
+		public bool TookBack() => JsSyncRuntime.Invoke<bool>("tookBack");
+
 		// whether the pointer can hover (a mouse); a touch screen can't, so what shows on hover there opens on a tap
 		public bool CanHover() => JsSyncRuntime.Invoke<bool>("canHover");