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

services/host_sensors.py

@@ -0,0 +1,95 @@
+"""Host/chassis temperature collectors: IPMI (iDRAC) + CPU coretemp.
+
+Used by the host-poller (separate process from the SAS poller). In-band IPMI
+via ipmitool (/dev/ipmi0) gives environmental sensors (Inlet/Exhaust/…); the
+kernel coretemp hwmon gives CPU package temps. IPMI is gated for serialization;
+coretemp is a cheap sysfs read.
+"""
+import asyncio
+import logging
+import re
+from pathlib import Path
+
+from services.hwgate import gate
+
+logger = logging.getLogger(__name__)
+
+HWMON = Path("/sys/class/hwmon")
+
+
+async def read_ipmi_temps() -> list[dict]:
+    """`ipmitool sdr type temperature` → [{name, temperature_c, status, kind}]."""
+    try:
+        async with gate():
+            proc = await asyncio.create_subprocess_exec(
+                "ipmitool", "sdr", "type", "temperature",
+                stdout=asyncio.subprocess.PIPE,
+                stderr=asyncio.subprocess.PIPE,
+            )
+            out, err = await proc.communicate()
+    except FileNotFoundError:
+        logger.warning("ipmitool not found")
+        return []
+    if proc.returncode != 0:
+        logger.warning("ipmitool failed: %s", err.decode(errors="replace").strip())
+        return []
+    return _parse_ipmi(out.decode(errors="replace"))
+
+
+def _parse_ipmi(text: str) -> list[dict]:
+    # e.g.  "Inlet Temp       | 04h | ok  |  7.1 | 23 degrees C"
+    #       "Temp             | 0Eh | ok  |  3.1 | 40 degrees C"  (CPU1)
+    sensors: list[dict] = []
+    for line in text.splitlines():
+        parts = [p.strip() for p in line.split("|")]
+        if len(parts) < 5:
+            continue
+        name, _sid, status, entity, reading = parts[:5]
+        m = re.search(r"(-?\d+(?:\.\d+)?)\s*degrees?\s*C", reading, re.IGNORECASE)
+        if not m:  # "no reading", "disabled", "ns", etc.
+            continue
+        temp = float(m.group(1))
+        kind = "env"
+        # Dell reports CPU temps as "Temp" under entity 3.x — relabel them.
+        if name.lower() == "temp" and entity.startswith("3."):
+            name = f"CPU {entity.split('.')[-1]}"
+            kind = "cpu"
+        sensors.append({
+            "name": name,
+            "temperature_c": temp,
+            "status": status or "ok",
+            "kind": kind,
+        })
+    return sensors
+
+
+def read_coretemp() -> list[dict]:
+    """CPU package temps from coretemp hwmon → [{name, temperature_c, kind}]."""
+    cpus: list[dict] = []
+    if not HWMON.is_dir():
+        return cpus
+    for hw in sorted(HWMON.iterdir()):
+        try:
+            if (hw / "name").read_text().strip() != "coretemp":
+                continue
+        except OSError:
+            continue
+        for label_f in sorted(hw.glob("temp*_label")):
+            try:
+                label = label_f.read_text().strip()
+            except OSError:
+                continue
+            if not label.lower().startswith("package id"):
+                continue
+            input_f = label_f.with_name(label_f.name.replace("_label", "_input"))
+            try:
+                milli = int(input_f.read_text().strip())
+            except (OSError, ValueError):
+                continue
+            pkg = label.split("id")[-1].strip()
+            cpus.append({
+                "name": f"CPU {pkg}",
+                "temperature_c": round(milli / 1000),
+                "kind": "cpu",
+            })
+    return cpus