Bump cryptography from 44.0.1 to 46.0.5 in /backend

Bumps [cryptography](https://github.com/pyca/cryptography) from 44.0.1 to 46.0.5.
- [Changelog](https://github.com/pyca/cryptography/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/pyca/cryptography/compare/44.0.1...46.0.5)

---
updated-dependencies:
- dependency-name: cryptography
  dependency-version: 46.0.5
  dependency-type: direct:production
...

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

backend/requirements.txt

@@ -31,7 +31,7 @@ celery==5.3.6
 redis==5.0.1
 
 # Security & Encryption
-cryptography==44.0.1  # Updated: Fixed NULL pointer dereference (was 42.0.0)
+cryptography==46.0.5  # Updated: Fixed NULL pointer dereference (was 42.0.0)
 
 # Notifications
 apprise==1.7.1