fix(monitoring): exclude shm from HostFilesystemDeviceError

node-exporter always reports device_error=1 for containerd sandbox shm
bind mounts (tmpfs), producing ~50 bogus critical alerts on the
kubevirt hosts. Verified against live metrics that no non-shm device
errors exist, so nothing real is filtered out.

Signed-off-by: Ryan Yin <xiaoyin_c@qq.com>

hosts/idols-aquamarine/monitoring/alert_rules/node-exporter.yml

@@ -136,7 +136,9 @@ groups:
             }}\n  LABELS = {{ $labels }}"
 
       - alert: HostFilesystemDeviceError
-        expr: "node_filesystem_device_error == 1"
+        # node-exporter always flags containerd/docker sandbox shm bind mounts
+        # (tmpfs) as device errors, exclude this known false positive.
+        expr: 'node_filesystem_device_error{device!="shm"} == 1'
         for: 0m
         labels:
           severity: critical