fix(notifications): only run waiting-reply foreground service while a reply is pending (#795)

The chat notification FGS — and its mandatory persistent 'Waiting for
Hermes replies' notification — was started on every ON_STOP of the chat
screen, even when nothing was in flight, and lingered at app startup.

Track a pending-reply flag on HermesWsClient (set when a prompt is
submitted and on any in-flight turn event, cleared on MessageComplete),
gate NotificationHelper.start() on it, and have the service retire
itself after delivering the reply notification in the background.
Replies sent from the notification re-arm the service for the
follow-up turn.

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/notification/NotificationReplyReceiver.kt

@@ -92,6 +92,15 @@ open class NotificationReplyReceiver : BroadcastReceiver() {
                             val repliedNotification = buildReplyNotification(context)
                             val manager = context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
                             manager.notify(ChatNotificationService.PENDING_NOTIFICATION_ID, repliedNotification)
+
+                            // The follow-up turn is now pending — keep the
+                            // foreground service alive if it retired after the
+                            // previous reply completed, so the next
+                            // MessageComplete still notifies while backgrounded
+                            // (issue #794). No-op when the app is foreground.
+                            if (!NotificationHelper.isAppInForeground()) {
+                                NotificationHelper.start(context)
+                            }
                         }
                     }
                 } catch (e: Exception) {