fix: add quser fallback for currently logged-on users

[kbaker827]

Summary

• Fixes the scanner returning no data on ~80% of machines where security event log only contains logon types 3/5 (network/service), not 2/10/11
• Adds a quser fallback that runs after the event log scan and captures the currently logged-on user if they weren't already found
• Guards against empty account names (adds $AccountName -ne "" check)
• Wraps quser in a try/catch and checks $LASTEXITCODE to handle machines with no logged-on user cleanly
• Collects results into a $Results ArrayList so the event log scan and quser results are emitted together

Root cause

On many machines (especially those accessed primarily via remote/network sessions), interactive logon events with types 2/10/11 are absent from the Security log. The scanner only looked at those types, so it returned nothing even though a user was actively logged on.

Test plan

• Run scanner on a machine with only type-3/5 events in the Security log — confirm the currently logged-on user is returned with LogonType = "Current User"
• Run scanner on a machine with normal type-2 events — confirm existing behavior is unchanged
• Run scanner on a machine with no logged-on user — confirm no errors and empty output

Closes #110