refactor: use ULIDs for items

[iuioiua]

Please pay attention to the migration script, as it's responsible for migrating all items and votes. I've also changed all instances of monotonicUlid() to ulid() at there appears to be a bug that prevents monotonicUlid() from respecting the seedTime parameter.

The migration can be simulated as follows:

1. Switch to main branch.
2. Run deno run db:reset.
3. Run deno run db:seed.
4. Run deno task start and navigate to http://localhost:8000.
5. Vote some items.
6. Note the voted items and the order of the items feed.
7. Switch to ulid-items branch.
8. Run deno run db:migrate.
9. Run deno task start and navigate to http://localhost:8000.
10. Check that the voted items and the order of the items feed are identical to those previously noted.

Closes #475
Closes #476

[kt3k]

I observed the increases of score count by 1 for the items I voted after running migration

[iuioiua]

@kt3k, I've made some tweaks. Try now.

[kt3k]

Confirmed it's fixed now 👍

[kt3k]

LGTM

[mbhrznr]

just gave the migration a spin.
works like a charm!
well done! 👏 👏