fix: clear resolved_at when reopening a status incident via appended update

server/internal/services/statusincidents.go

@@ -228,6 +228,13 @@ func AppendStatusIncidentUpdate(instanceID, incidentID, status, body, author str
 	set := bson.M{"status": status, "updated_at": upd.At}
 	if status == models.IncidentResolved || status == models.MaintenanceCompleted {
 		set["resolved_at"] = upd.At
+	} else {
+		// Reopening via an appended update must clear a previously-set
+		// resolved_at the same way UpdateStatusIncident does — otherwise a
+		// resolved incident reopened to "monitoring" keeps a stale resolved_at
+		// and silently drops off ListStatusIncidentsForPage once started_at
+		// ages past the since cutoff, because none of its $or clauses match.
+		set["resolved_at"] = nil
 	}
 
 	ctx, cancel := spCtx()