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>

unifi/scheduler.py

@@ -49,8 +49,8 @@ async def _do_poll(app: "Quart") -> None:
         )
         try:
             await _client.login()
-        except Exception:
-            logger.exception("UniFi initial login failed")
+        except Exception as exc:
+            logger.warning("UniFi initial login failed: %s", exc)
             _client = None
             return
 
@@ -58,8 +58,8 @@ async def _do_poll(app: "Quart") -> None:
         health = await _client.get_health()
         clients = await _client.get_active_clients()
         devices = await _client.get_devices()
-    except Exception:
-        logger.exception("UniFi poll failed — will retry next tick")
+    except Exception as exc:
+        logger.warning("UniFi poll failed — will retry next tick: %s", exc)
         _client = None  # force re-auth on next tick
         return
 
@@ -185,8 +185,8 @@ async def _do_poll(app: "Quart") -> None:
     # ── Expanded data (best-effort, failures don't abort core poll) ───────────
     try:
         await _do_expanded(app, scraped_at)
-    except Exception:
-        logger.exception("UniFi expanded poll failed")
+    except Exception as exc:
+        logger.warning("UniFi expanded poll failed: %s", exc)
 
 
 async def _do_expanded(app: "Quart", scraped_at: datetime) -> None: