Prevent OS sleep and display blanking while SDR is running

Add PowerInhibit.pas with InhibitSleep/UninhibitSleep:
- Windows: SetThreadExecutionState (kernel32, no child process)
- macOS: caffeinate -d -i -s -w <PID> (auto-exits on crash via -w flag)
- Linux: systemd-inhibit with kill-0 poll loop (releases within 5s on crash)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ewsdr.lpi

@@ -229,6 +229,10 @@
         <Filename Value="PlatformUtils.pas"/>
         <IsPartOfProject Value="True"/>
       </Unit>
+      <Unit>
+        <Filename Value="PowerInhibit.pas"/>
+        <IsPartOfProject Value="True"/>
+      </Unit>
       <Unit>
         <Filename Value="BoardUtils.pas"/>
         <IsPartOfProject Value="True"/>