fix(scripts): resolve lint issues in setup-oci-public.py

- Make file executable (EXE001)
- Add explicit check=False to all subprocess.run calls (PLW1510)
- Replace blind Exception catches with specific types (BLE001/S110)
- Use mode="wb" for binary cert tempfile write (ty overload)
- Add type narrowing assert for lb_ip (ty invalid-argument-type)
- Add noqa for intentional naive datetime parse (DTZ007)

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

Author: ericfitz