Split into dedicated hardware poller + read-only consumers

Rearchitect so a single poller process is the sole owner of all SAS/SMART/
SES hardware I/O, serialized behind one gate and paced, writing results to
Redis. The API/web and MQTT publisher become pure Redis readers — they no
longer issue any subprocess and can restart freely without touching the bus.

This addresses backplane/expander stress from concurrent + restart-triggered
SMART/SES storms (the prior model re-ran a hardware sweep on every container
start, and polled sg_ses 0x02+0x07 every 60s; 0x07 errored on the IOM6/
Xyratex expanders).

- poller.py: paced sweep (inventory, SMART per-drive w/ gap, SES 0x02, ZFS,
  host/MegaRAID), startup jitter, single-instance Redis lock, LED-queue worker
- services/hwgate.py: global serialization semaphore (POLL_CONCURRENCY=1)
- services/store.py: Redis as the only producer<->consumer interface + LED queue
- services/health.py: shared drive-health classifier (fixes overview double-count)
- gate smartctl/sg_ses/zpool/ledctl; drop sg_ses 0x07 from the hot path
- routers + temps read-only from the store; main.py drops the in-process poller
- compose: 3 services (privileged poller + unprivileged app + redis) w/ pacing knobs

routers/enclosures.py

@@ -1,24 +1,23 @@
 from fastapi import APIRouter, HTTPException
 
 from models.schemas import Enclosure, SlotInfo
-from services.enclosure import discover_enclosures, list_slots
+from services import store
 
 router = APIRouter(prefix="/api/enclosures", tags=["enclosures"])
 
 
 @router.get("", response_model=list[Enclosure])
 async def get_enclosures():
-    """Discover all SES enclosures."""
-    return discover_enclosures()
+    """List all discovered SES enclosures (from the poller inventory)."""
+    inventory = await store.get_inventory()
+    return [Enclosure(**e) for e in inventory.get("enclosures", [])]
 
 
 @router.get("/{enclosure_id}/drives", response_model=list[SlotInfo])
 async def get_enclosure_drives(enclosure_id: str):
-    """List all drive slots for an enclosure."""
-    slots = list_slots(enclosure_id)
-    if not slots:
-        # Check if the enclosure exists at all
-        enclosures = discover_enclosures()
-        if not any(e["id"] == enclosure_id for e in enclosures):
-            raise HTTPException(status_code=404, detail=f"Enclosure '{enclosure_id}' not found")
-    return slots
+    """List all drive slots for an enclosure (from the poller inventory)."""
+    inventory = await store.get_inventory()
+    for enc in inventory.get("enclosures", []):
+        if enc["id"] == enclosure_id:
+            return [SlotInfo(**s) for s in enc.get("slots", [])]
+    raise HTTPException(status_code=404, detail=f"Enclosure '{enclosure_id}' not found")