fix: pass pointer to xorm Update to avoid hash panic in transaction mode

In transaction mode, xorm stores the bean argument as a map key in
afterUpdateBeans. Since Task contains slices and maps (unhashable
types), passing a Task value causes "hash of unhashable type" panic.
Passing a pointer (&ot) fixes this since pointers are always hashable.

pkg/models/tasks.go

@@ -1382,7 +1382,7 @@ func (t *Task) updateSingleTask(s *xorm.Session, a web.Auth, fields []string) (e
 
 	_, err = s.ID(t.ID).
 		Cols(colsToUpdate...).
-		Update(ot)
+		Update(&ot)
 	*t = ot
 	if err != nil {
 		return err