security: bump vulnerable Python dependencies

- litellm >=1.83.0 (critical: OIDC auth bypass, high: privilege escalation)
- requests >=2.33.0 (medium: insecure temp file reuse)
- aiohttp >=3.13.4 (4 medium + 6 low: header injection, SSRF, DoS)
- pygments >=2.20.0 (low: ReDoS)
- cryptography >=46.0.6 (low: incomplete DNS constraint)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>