Add host-poller: chassis IPMI/iDRAC + CPU + on-metal drive temps

New third producer container (host-poller) owning the server chassis
subsystem, separate from the SAS-shelf poller:
- services/host_sensors.py: in-band IPMI (ipmitool sdr) for Inlet/Exhaust/etc.
  + CPU package temps from coretemp hwmon
- host_poller.py: own single-instance lock + heartbeat (host_poll keys),
  restart-storm guard, paced; writes jbod:host_sensors + jbod:host_drives
- move host/on-metal drive collection off the SAS poller to host-poller
  (reads jbod:zfs_map for annotation)
- store: generalized lock/meta with a key param; host_sensors + host-poll keys
- mqtt_publisher: publish env/CPU/host-drive temps as entities on the hub
  device (JBOD Monitor)
- Dockerfile host-poller target (ipmitool+smartmontools); compose.infra adds
  host-poller; build.sh gains host-poller/all

poller.py

@@ -23,7 +23,6 @@ import time
 from services import store
 from services.cache import close_cache, init_cache, redis_available
 from services.enclosure import discover_enclosures, get_enclosure_status, list_slots
-from services.host import get_host_drives
 from services.leds import run_led
 from services.smart import _run_smartctl, sg_ses_available, smartctl_available
 from services.zfs import get_zfs_pool_map
@@ -86,12 +85,7 @@ async def sweep() -> None:
         except Exception as e:
             errors.append(f"ses:{enc['id']}:{e}")
 
-    # 5. Host (non-enclosure) drives + MegaRAID (gated, reuses pool_map).
-    try:
-        host_drives = await get_host_drives(pool_map)
-        await store.set_host_drives(host_drives)
-    except Exception as e:
-        errors.append(f"host:{e}")
+    # NOTE: host/on-metal drives are owned by the separate host-poller now.
 
     # 6. Inventory + heartbeat.
     await store.set_inventory({"enclosures": inv_enclosures, "ts": store.now()})