address review feedback

- Discard the export row when an export fails before or during ffmpeg, so it doesn't stay in progress until a restart
- Skip the empty thumbnail path when discarding a failed export
- Measure preview clip duration from the clamped start
- Default live player volume to 1 when the group has no saved setting
- Clear the unsaved registration message when notification registration fails
- Keep a highlight timer per trigger
- Remove the severity order_by in /review, which the start_time order_by replaced

web/src/components/config-form/sectionExtras/NotificationsSettingsExtras.tsx

@@ -415,6 +415,7 @@ export default function NotificationsSettingsExtras({
               pushSubscription.unsubscribe();
               workerRegistration.unregister();
               setRegistration(null);
+              removeMessage("notification_settings", "registration");
             });
         })
         .catch(() => {
@@ -423,9 +424,10 @@ export default function NotificationsSettingsExtras({
           });
           workerRegistration.unregister();
           setRegistration(null);
+          removeMessage("notification_settings", "registration");
         });
     },
-    [addMessage, publicKey, t],
+    [addMessage, removeMessage, publicKey, t],
   );
 
   useEffect(() => {