Auto-cleanup Nouveau indexes

## Summary / Desired Behaviour / Possible Solution

Make Smoosh automatically [cleanup Nouveau indexes](https://docs.couchdb.org/en/latest/api/database/cleanup.html#post--db-_nouveau_cleanup) to optimize disk usage.

## Additional context

[Related Slack thread](https://couchdb.slack.com/archives/C49LEE7NW/p1732102415451979)
