Add reboot API facade helper

[spyroot]

Summary

• add a typed RebootResult plus a reboot() facade wrapper over the existing reboot command
• make facade resets preview by default, with confirm=True required for execution
• cover the wrapper with unit tests and GB300 corpus-backed dry-run coverage through the command registry

Tests

• conda run -n idrac_ctl pytest -q tests/test_api_facade.py
• conda run -n idrac_ctl ruff check redfish_ctl/api.py tests/test_api_facade.py
• conda run -n idrac_ctl pytest -q

[spyroot]

Reviewed and approved on the merits — reboot previews by default (confirm=False -> dry_run=True), waits only when confirmed, RebootResult is frozen, and tests assert GET-only in the default path. Can't merge as-is: the GPU/NTP facade helpers landed on main first, so this now conflicts on redfish_ctl/api.py and tests/test_api_facade.py. Please rebase onto main and re-apply the reboot helper and its tests after the new helpers. Clean merge after that.