fix(beszel): GPU-LXC temperature alerts watch the GPU, not the hypervisor CPU

nh3-ml1's first Temperature alert (2026-09-25 2105, 88.8 C) was nh3-pve's CPU
package during the nightly vzdump; the GPU sat at 47 C. hwmon is not namespaced,
so an LXC's agent reports its host's coretemp sensors under the LXC's name.

- hosts/{nh3,esh}-ml1.yaml: SENSORS=-coretemp_*,acpitz (blacklist); GPU and
  NVMe temperatures verified still reported.
- Hub: Temperature >95 C / 5 m on nh3-pve and esh-pve for the CPUs (i9-13900H
  TjMax 100 C; nh3-pve 2-hour averages reach 88 C on busy days).
- nh3-pve README: runs warmer than esh-pve; workload confounds it, check
  airflow on the next visit.

servers/nh3-pve/README.md

@@ -117,6 +117,16 @@ not power back on by itself.
   oops and has run fine, so it is benign so far: only the BT worker dies. The fix
   is to blacklist `btusb` on both hypervisors. That is not done, because it only
   takes effect at the next boot.
+- **Runs warmer than esh-pve, its twin (Beszel, 2026-09-15 → 09-25).**
+  - nh3-pve's CPU package: median of 2-hour averages 76 °C, peak 2-hour average
+    88 °C (2026-09-23, CPU ~15%).
+  - esh-pve: medians 52–55 °C, peak 20-min average 78 °C.
+  - During the 2026-09-25 2100 vzdump, the 1-minute samples reached 90 °C at
+    13–21% CPU. They were back to 61 °C once the job finished.
+  - Workload is a confound: nh3-pve usually carries more load, so this does not
+    prove a cooling fault. Worth checking airflow and dust on the next visit.
+  - TjMax is 100 °C. The Beszel CPU alert on this host is set at >95 °C for
+    5 minutes.
 - **lxc-pve 6.0.0-1 → 6.0.0-2** (2026-09-25 1533, that one package only). This is
   Proxmox fix #7006. Without it, runc 1.5 inside a nesting CT fails every
   `docker run`. `playbooks/gpu-lxc.yaml` now upgrades it first.