delete bolt.
aside from other bugs that have happened before, this one:
https://cdn.satellite.earth/25a4bc5c9fd7617cdcba309a552d227283fb2d36aa75f47b12c0b83510c4de88.png
is caused directly by bbolt's `unsafe` usage.
something wrong is not right inside bbolt's codebase and I don't think it's worth trying to solve it.
bolt is kinda annoying anyway, like it blocks the database and makes things hang forever, has some
weird locking and stuff. so if people want a pure-go setup they can use badger, and if they want better
read performance they should use LMDB. bolt is unnecessary.
