App Book file size filter doesn't work + is only ever treated as an OR

[zachyale]

What went wrong?

When using the app book file size filter on the book browser, AND is never handled properly on the F/E, and the B/E 500s.

How can we reproduce it?

1. Open the book browser and the developer network monitor
2. Try to filter by file size
3. Note the 500, note the request is always as an OR

What Build of Grimmory are you on?

Stable

Your setup

• Grimmory stable

Screenshots or error messages (optional)

No response

Before submitting

• I've searched existing discussions and this hasn't been reported yet
• I've reviewed this report and have completed it as fully as I can

[zachyale]

Moved to #808