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>

conf/ipmi-fancontrol.conf.example

@@ -0,0 +1,17 @@
+# Credentials for the BMC user driving ipmi-fancontrol-manual / ipmi-fancontrol-auto.
+#
+# Copy to conf/ipmi-fancontrol.conf next to the scripts and lock it down:
+#   cp conf/ipmi-fancontrol.conf.example conf/ipmi-fancontrol.conf
+#   chmod 0600 conf/ipmi-fancontrol.conf
+#
+# The scripts look for it relative to their own location, so this works both in a
+# checkout and deployed at /opt/ergosteur. Override with IPMI_FANCONTROL_CONFIG.
+
+IPMI_HOST=169.254.0.1
+IPMI_USER=fancontrol
+
+# Read by ipmitool -E, so it never appears in the process table.
+IPMI_PASSWORD=changeme
+
+# Fan speed applied in manual mode, as a raw hex byte (0x15 = 21%).
+FAN_SPEED=0x15