Add IPMI fan control scripts, reading credentials from conf/

ipmi-fancontrol.service pins the fans to a fixed speed on start and hands
control back to the BMC's automatic curve on stop, to quiet the chassis.

BMC credentials are read from conf/ipmi-fancontrol.conf, resolved relative
to the scripts themselves so the tree stays self-contained whether it is run
from a checkout or from /opt/ergosteur. See conf/ipmi-fancontrol.conf.example.

Use ipmitool -E rather than -P so the password is passed via the environment
instead of argv, where any local user could read it out of ps.

docker-idrac.sh is the alternative temperature-aware controller.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ipmi-fancontrol-auto

@@ -0,0 +1,25 @@
+#!/bin/sh
+# Hand fan control back to the BMC's automatic curve.
+# Paired with ipmi-fancontrol-manual via ipmi-fancontrol.service.
+set -eu
+
+SCRIPT_DIR=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+CONFIG=${IPMI_FANCONTROL_CONFIG:-$SCRIPT_DIR/conf/ipmi-fancontrol.conf}
+
+if [ ! -r "$CONFIG" ]; then
+    echo "Error: cannot read $CONFIG" >&2
+    echo "Copy conf/ipmi-fancontrol.conf.example there and fill in the BMC credentials." >&2
+    exit 1
+fi
+
+. "$CONFIG"
+
+: "${IPMI_HOST:?not set in $CONFIG}"
+: "${IPMI_USER:?not set in $CONFIG}"
+: "${IPMI_PASSWORD:?not set in $CONFIG}"
+
+# ipmitool -E reads the password from IPMI_PASSWORD, keeping it out of argv.
+export IPMI_PASSWORD
+
+# Re-enable automatic fan control.
+ipmitool -I lanplus -H "$IPMI_HOST" -U "$IPMI_USER" -E raw 0x30 0x30 0x01 0x01