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

main.py

@@ -10,9 +10,10 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.staticfiles import StaticFiles
 
 from models.schemas import HealthCheck
-from routers import drives, enclosures, leds, overview
+from routers import drives, enclosures, leds, overview, temps
 from services.cache import cache_set, close_cache, init_cache, redis_available
 from services.enclosure import discover_enclosures, list_slots
+from services.mqtt_publisher import MqttPublisher, _PAHO_AVAILABLE, mqtt_enabled
 from services.smart import SMART_CACHE_TTL, _run_smartctl, sg_ses_available, smartctl_available
 from services.zfs import get_zfs_pool_map
 
@@ -26,6 +27,8 @@ SMART_POLL_INTERVAL = int(os.environ.get("SMART_POLL_INTERVAL", "90"))
 
 _tool_status: dict[str, bool] = {}
 _poll_task: asyncio.Task | None = None
+_mqtt_task: asyncio.Task | None = None
+_mqtt_publisher: MqttPublisher | None = None
 
 
 async def smart_poll_loop():
@@ -77,7 +80,7 @@ async def smart_poll_loop():
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
-    global _poll_task
+    global _poll_task, _mqtt_task, _mqtt_publisher
     # Startup
     _tool_status["smartctl"] = smartctl_available()
     _tool_status["sg_ses"] = sg_ses_available()
@@ -95,9 +98,31 @@ async def lifespan(app: FastAPI):
     if redis_available():
         _poll_task = asyncio.create_task(smart_poll_loop())
 
+    # Optional MQTT publisher for Home Assistant (opt-in via MQTT_HOST).
+    _tool_status["mqtt"] = False
+    if mqtt_enabled():
+        if not _PAHO_AVAILABLE:
+            logger.warning("MQTT_HOST set but paho-mqtt not installed — MQTT disabled")
+        else:
+            try:
+                _mqtt_publisher = MqttPublisher()
+                _mqtt_publisher.start()
+                _mqtt_task = asyncio.create_task(_mqtt_publisher.run())
+                _tool_status["mqtt"] = True
+            except Exception as e:
+                logger.error("Failed to start MQTT publisher: %s", e)
+
     yield
 
     # Shutdown
+    if _mqtt_task is not None:
+        _mqtt_task.cancel()
+        try:
+            await _mqtt_task
+        except asyncio.CancelledError:
+            pass
+    if _mqtt_publisher is not None:
+        _mqtt_publisher.stop()
     if _poll_task is not None:
         _poll_task.cancel()
         try:
@@ -125,6 +150,7 @@ app.include_router(enclosures.router)
 app.include_router(drives.router)
 app.include_router(leds.router)
 app.include_router(overview.router)
+app.include_router(temps.router)
 
 
 @app.get("/api/health", response_model=HealthCheck, tags=["health"])