build(deps): bump fpdf2 from 2.7.9 to 2.8.2 in /backend

Bumps [fpdf2](https://github.com/py-pdf/fpdf2) from 2.7.9 to 2.8.2.
- [Release notes](https://github.com/py-pdf/fpdf2/releases)
- [Changelog](https://github.com/py-pdf/fpdf2/blob/master/CHANGELOG.md)
- [Commits](https://github.com/py-pdf/fpdf2/compare/2.7.9...2.8.2)

---
updated-dependencies:
- dependency-name: fpdf2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -55,7 +55,7 @@ einops==0.8.0
 
 ftfy==6.2.3
 pypdf==4.3.1
-fpdf2==2.7.9
+fpdf2==2.8.2
 pymdown-extensions==10.11.2
 docx2txt==0.8
 python-pptx==1.0.0