docs(known-issues): mark central-report singleton-hang fix as committed (was stale 'pending commit')

The HOST-021 fix (AkkaHostedService.GetOrCreateActorSystem + AddSingleton<ActorSystem>
in Program.cs/SiteServiceRegistration.cs) is committed and live on main; the tracker
still read 'pending commit' / 'Fix (pending, task #48)'. Status corrected.

docs/known-issues/2026-06-05-central-report-pages-singleton-query-hang.md

@@ -1,6 +1,6 @@
 # Central report pages hang ~30s — NotificationOutbox / SiteCallAudit singleton query Asks never reply
 
-**Status:** FIXED — verified 2026-06-05 (pending commit) · **Severity:** High (real users see 30s page loads) · **Found:** 2026-06-05
+**Status:** FIXED — verified 2026-06-05; committed & live on `main` (confirmed 2026-06-24: `AkkaHostedService.GetOrCreateActorSystem()` + `AddSingleton<ActorSystem>` registrations present in HEAD) · **Severity:** High (real users see 30s page loads) · **Found:** 2026-06-05
 **Components:** Notification Outbox (#21), Site Call Audit (#22), Central UI (#9), Host/cluster (#15/#13)
 
 ## FIX APPLIED & VERIFIED (2026-06-05)
@@ -73,7 +73,7 @@ the `ActorSystem` is simply **dead** by the time a page queries it. "Determinist
 restart and full redeploy" is fully explained: it is a DI-lifetime code defect that
 re-triggers on the first post-`Up` health probe every boot.
 
-**Fix (pending, task #48):** stop the container from disposing the externally-owned
+**Fix (applied 2026-06-05 — see "FIX APPLIED & VERIFIED" above):** stop the container from disposing the externally-owned
 `ActorSystem`. It must be resolvable from DI as the live instance (the kit calls
 `GetService<ActorSystem>()`), re-readable (must not cache `null` during warmup), and never
 disposed by a child scope. A `Transient`/`Scoped` factory returning the `IDisposable` system