fix(duo): force update check when --update flag is used

Summary

The --update flag was not forcing an immediate update check. It was respecting the 24-hour delay, preventing users from getting the latest version on demand.

Changes

Modified performUpdateCheck() to accept a forceCheck parameter:

• When called from handleUpdate() (triggered by --update flag): pass true to force immediate check
• When called from checkForUpdates() (background check): pass env var value for optional override

Testing

• All existing tests pass
• Verified API returns latest version (8.72.0)
• Confirmed the fix allows --update to bypass the 24h delay