logind: Set InhibitDelayMaxSec=300 to allow Supervisor graceful shutdown (#4577)

Supervisor takes a logind delay inhibitor lock on startup and releases it
after gracefully stopping all add-ons, Home Assistant Core, and plugins in
the correct order. The default 5s window is far too short — Core alone can
take 40+ seconds to stop. 300s gives enough headroom for a clean shutdown.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: agners

buildroot-external/rootfs-overlay/etc/systemd/logind.conf

@@ -17,7 +17,7 @@
 #KillUserProcesses=yes
 #KillOnlyUsers=
 #KillExcludeUsers=root
-#InhibitDelayMaxSec=5
+InhibitDelayMaxSec=300
 HandlePowerKey=ignore
 HandlePowerKeyLongPress=poweroff
 HandleRebootKey=ignore