Fixed news subscription scheduling regressions from #4492: a manual "Run Now" whose research later failed no longer pushes the subscription out a full refresh interval (it is reset to due so the scheduler retries), the run-now request no longer holds the encrypted-DB session open across the research-start HTTP call, and the subscription folder-update PUT route now keeps `status` authoritative (an `is_active` toggle pauses correctly instead of being ignored by the scheduler). The same folder-update route was also repaired — it previously failed on every call due to a bad relative import and a missing serializer.
