Split host-poller into separate env (IPMI/CPU) and drive (SMART) loops

Two concurrent loops in one process sharing the lock + hardware gate (IPMI and
SMART never run concurrently) but on separate schedules: env every
HOST_ENV_INTERVAL (60s, responsive inlet/CPU) and drives every
HOST_DRIVE_INTERVAL (300s, gentle SMART). Each loop has its own heartbeat
(env_meta/drive_meta) + restart-storm guard.

compose.infra.yml

@@ -52,7 +52,8 @@ services:
       - REDIS_HOST=127.0.0.1
       - REDIS_PORT=6379
       - REDIS_DB=0
-      - HOST_POLL_INTERVAL=60
+      - HOST_ENV_INTERVAL=60     # IPMI/iDRAC + CPU — responsive (inlet temp 1/min)
+      - HOST_DRIVE_INTERVAL=300  # on-metal SMART — gentle, isolated from env
       - POLL_DRIVE_GAP=0.5
       - POLL_CONCURRENCY=1
       - POLL_STARTUP_JITTER=10