Add per-enclosure temperature metrics + Home Assistant MQTT publisher

- enclosure: fetch SES element descriptor page (0x07) and label temp/fan/
  psu/voltage elements with human-readable names
- temps service + /api/temps: per-enclosure hotspot (max across SES sensors
  and housed drive temps) plus named SES sensor list
- mqtt_publisher: paho-mqtt with HA discovery (device per enclosure, hotspot
  + per-sensor entities), LWT availability, opt-in via MQTT_HOST
- secrets: OpenBao KV v2 reader; MQTT creds sourced from secret/home_assistant
  with env fallback
- compose/requirements/README updated

services/temps.py

@@ -0,0 +1,84 @@
+"""Per-enclosure temperature aggregation.
+
+Builds a compact snapshot of enclosure temperatures suitable for Home
+Assistant: each named SES temperature sensor plus a derived per-enclosure
+hotspot (the hottest reading across SES sensors *and* the drives housed in
+that enclosure — drive temps are usually the real hotspot signal).
+"""
+import asyncio
+import logging
+import socket
+
+from services.enclosure import discover_enclosures, get_enclosure_status, list_slots
+from services.smart import get_smart_data
+
+logger = logging.getLogger(__name__)
+
+
+def get_node_id() -> str:
+    """Stable identifier for this monitor instance (defaults to hostname)."""
+    import os
+
+    return os.environ.get("MQTT_NODE_ID") or socket.gethostname() or "jbod-monitor"
+
+
+async def build_temp_snapshot() -> dict:
+    """Collect per-enclosure temperature metrics for all enclosures."""
+    enclosures = discover_enclosures()
+
+    async def _health(enc):
+        if enc.get("sg_device"):
+            return await get_enclosure_status(enc["sg_device"])
+        return None
+
+    health_results = await asyncio.gather(
+        *[_health(enc) for enc in enclosures], return_exceptions=True
+    )
+
+    out_enclosures: list[dict] = []
+    for enc, health in zip(enclosures, health_results):
+        if isinstance(health, Exception):
+            logger.warning("SES health failed for %s: %s", enc["id"], health)
+            health = None
+
+        sensors: list[dict] = []
+        sensor_temps: list[float] = []
+        if isinstance(health, dict):
+            for t in health.get("temps", []):
+                temp = t.get("temperature_c")
+                sensors.append({
+                    "index": t["index"],
+                    "name": t.get("name"),
+                    "status": t.get("status", "Unknown"),
+                    "temperature_c": temp,
+                })
+                if isinstance(temp, (int, float)) and temp > 0:
+                    sensor_temps.append(float(temp))
+
+        # Drive temperatures for drives housed in this enclosure.
+        drive_temps: list[float] = []
+        devices = [s["device"] for s in list_slots(enc["id"]) if s.get("device")]
+        if devices:
+            smart_results = await asyncio.gather(
+                *[get_smart_data(d) for d in devices], return_exceptions=True
+            )
+            for res in smart_results:
+                if isinstance(res, Exception):
+                    continue
+                data, _hit = res
+                temp = data.get("temperature_c")
+                if isinstance(temp, (int, float)) and temp > 0:
+                    drive_temps.append(float(temp))
+
+        all_temps = sensor_temps + drive_temps
+        out_enclosures.append({
+            "id": enc["id"],
+            "vendor": enc.get("vendor", ""),
+            "model": enc.get("model", ""),
+            "hotspot_c": max(all_temps) if all_temps else None,
+            "drive_max_c": max(drive_temps) if drive_temps else None,
+            "drive_temp_count": len(drive_temps),
+            "sensors": sensors,
+        })
+
+    return {"node": get_node_id(), "enclosures": out_enclosures}