Modsecurity: Book Cover 403 Forbidden

### Problem

As requested by @mekarpeles at https://github.com/internetarchive/openlibrary/issues/12718, I'm creating a new issue. More than once (most recently today), I've gotten a "Book Cover 403 Forbidden" message when I tried to upload book covers from my computer to the following editions:

https://openlibrary.org/books/OL62382445M/Addicted_to_Anxiety
https://openlibrary.org/books/OL33666561M/Ten_Times_Happier

### Reproducing the bug

1. Go to edition [OL62382445M](https://openlibrary.org/books/OL62382445M/Addicted_to_Anxiety) [ISBN 9781250439970] or [OL33666561M](https://openlibrary.org/books/OL33666561M/Ten_Times_Happier) (ISBN 9780008378240);
2. Click "Edit";
3. Click "Add Cover Image";
4. Click "Choose File";
5. Navigate to and select the appropriate cover;
6. Click "Upload."

* Expected behavior: The cover should have been uploaded to the edition.
* Actual behavior: Received a "Book Cover 403: Forbidden" message (see screenshots above).

### Context

- Browser (Chrome, Safari, Firefox, etc): DuckDuckGo and Google Chrome
- OS (Windows, Mac, etc): Windows 11
- Logged in (Y/N): Yes
- Environment (prod, dev, local): prod

### Breakdown

Implementation Details (for maintainers)

#### Requirements Checklist
* [ ]

#### Related files

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#### Stakeholders

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#### Instructions for Contributors

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Start by reproducing the cover upload failure on the two linked editions in production, using the listed browser and Windows context. Trace the upload path and ModSecurity handling for the "Book Cover 403: Forbidden" response; done means valid cover uploads succeed for these editions without the 403.

Written by the indexing model from the issue text.