Migration to fix script_level ordering bug in database

The existing databases are in a stuck position with incorrectly-ordered levels. This migration will reset all of the stages, so that the positions of its stage levels can be regenerated from scratch.
@wjordan sorry if this is a stupid question, still getting the lay of the land with the import logic—does a full delete/re-create potentially pose any risks to existing data on prod? i.e., will `script_level`s still have the same IDs and reference the same `script`s after a destroy/import of scripts?