fix(security): update vulnerable dependencies in celery example
Update pinned versions in examples/celery/requirements.txt to resolve
13 known security vulnerabilities (1 HIGH, 11 MEDIUM, 1 LOW):
- werkzeug 2.3.3 -> 3.1.6 (CVE-2024-34069, CVE-2023-46136, CVE-2024-49766, CVE-2024-49767, CVE-2025-66221, CVE-2026-21860, CVE-2026-27199)
- jinja2 3.1.2 -> 3.1.6 (CVE-2024-22195, CVE-2024-34064, CVE-2024-56201, CVE-2024-56326, CVE-2025-27516)
- flask 2.3.2 -> 3.1.3 (CVE-2026-27205)
Also bumps transitive deps for compatibility:
- blinker 1.6.2 -> 1.9.0
- itsdangerous 2.1.2 -> 2.2.0
- markupsafe 2.1.2 -> 3.0.3
330fc07272