Secfix Agent: report the inactivity timeout for screen lock, not only the grace period

The "Configured Screen Lock" value in the Secfix Agent shows the grace period: the time after the screen turns off before a password is required. On my macOS, this shows as 0.0833 min on the Computers page.

Problem: The grace period doesn't show how long a device can stay idle before it locks. A Mac with the display set to never turn off would still report 5 seconds.

Requested improvements

1. Show the inactivity timeout, meaning how long a device can sit idle before the screen turns off or locks.

2. Flag it against a configurable threshold (e.g. ≤ 5 min) so admins can see compliance at a glance.

3. Check battery and plugged-in settings separately. macOS and Windows allow different timers for each, so a device can be compliant on battery but not when plugged in. Reporting the less strict of the two would be a reasonable default.