Fix `@fedify/next` can't import and other problems

[2chanhaeng]

Summary

@fedify/next has some errors. I'll pr the hotfix.

Expected Behavior

@fedify/next works properly with Next.js apps.

Actual Behavior

• Typescript language server doesn't find modules.
• Errors cuased by using notFound

Environment

All

Logs / Screenshots

Steps to Reproduce

Create Next.js app and using @fedify/next

[ThisIsMissEm]

Could you also share the errors here so we have a record of them? Thanks!