Add temperature-aware MD1200 fan control

das_fanctl.sh reads drive temps via smartctl (falling back to the EMM
backplane sensors), interpolates a fan percentage, and re-sends _shutup
on a 5s keepalive so the shelf does not revert to full speed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

fan_speed.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Fan_Speed service
+
+[Service]
+ExecStart=/bin/bash -c /root/fan_speed/fan_speed.sh
+
+[Install]
+WantedBy=multi-user.target