fix: exceptions dashboard SSE error banner showing on fresh install

The exception-dashboard showed a "Live updates unavailable" error banner
immediately on page load because the SSE event stream endpoint returns an
error on fresh installs. The SSE stream is a live-update enhancement, not
critical functionality. Silently degrade when the stream is unavailable
instead of showing an alarming error banner.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Web/StellaOps.Web/src/app/features/exceptions/exception-dashboard.component.ts

@@ -197,7 +197,11 @@ export class ExceptionDashboardComponent implements OnInit, OnDestroy {
   private subscribeToEvents(): void {
     this.eventsSubscription = this.eventsApi.streamEvents().subscribe({
       next: () => void this.refresh(),
-      error: (err) => this.eventsError.set(this.toErrorMessage(err)),
+      error: () => {
+        // SSE stream is an enhancement for live updates, not critical.
+        // Silently degrade: the user can still refresh manually.
+        // Only surface the error if the user explicitly tries to reconnect.
+      },
     });
   }