fix: reduce log noise and guard against non-dict SNMP devices

- SNMP scheduler: skip non-dict entries in devices list (prevents AttributeError)
- UPS scheduler: downgrade NutError from exception to warning (expected when NUT not running)
- UniFi scheduler: downgrade login/poll failures from exception to warning (expected when controller unreachable)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

snmp/scheduler.py

@@ -0,0 +1,78 @@
+# plugins/snmp/scheduler.py
+from __future__ import annotations
+import asyncio
+import logging
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from quart import Quart
+
+from fabledscryer.core.scheduler import ScheduledTask
+
+logger = logging.getLogger(__name__)
+
+
+def make_poll_task(app: "Quart") -> ScheduledTask:
+    interval = app.config["PLUGINS"]["snmp"].get("poll_interval_seconds", 60)
+
+    async def poll() -> None:
+        await _do_poll(app)
+
+    return ScheduledTask(
+        name="snmp_poll",
+        coro_factory=poll,
+        interval_seconds=int(interval),
+        run_on_startup=True,
+    )
+
+
+async def _do_poll(app: "Quart") -> None:
+    from datetime import datetime, timezone
+    from .poller import poll_device_sync
+    from fabledscryer.core.alerts import record_metric
+
+    devices: list[dict] = app.config["PLUGINS"]["snmp"].get("devices", [])
+    if not devices:
+        return
+
+    loop = asyncio.get_event_loop()
+    now = datetime.now(timezone.utc)
+
+    async with app.db_sessionmaker() as session:
+        async with session.begin():
+            for device in devices:
+                if not isinstance(device, dict):
+                    continue
+                name = device.get("name") or device.get("host", "unknown")
+                host = device.get("host", "")
+                port = int(device.get("port", 161))
+                community = device.get("community", "public")
+                version = str(device.get("version", "2c"))
+                oids = device.get("oids", [])
+
+                if not host or not oids:
+                    continue
+
+                try:
+                    readings = await loop.run_in_executor(
+                        None,
+                        poll_device_sync,
+                        host, port, community, version, oids,
+                    )
+                except Exception:
+                    logger.exception("SNMP poll failed for device %s (%s)", name, host)
+                    continue
+
+                for label, value in readings.items():
+                    await record_metric(
+                        session=session,
+                        source_module="snmp",
+                        resource_name=name,
+                        metric_name=label,
+                        value=value,
+                    )
+
+                if readings:
+                    logger.debug("SNMP polled %s (%s): %d OID(s)", name, host, len(readings))
+                else:
+                    logger.debug("SNMP polled %s (%s): no readings", name, host)