Optional aGate address on the API (home-LAN direct connect)

AgateClient takes address= default; attach_local accepts
address/host/gateway_ip per call with join control. An explicit
address skips the SoftAP radio join by default (join=True forces
it). derive_hotspot_credentials and join_device_hotspot accept a
gateway_ip override. battery/power host defaults now use
DEVICE_GATEWAY_IP. Verified live at 192.168.1.142:9000.

franklinwh_agate_client/power.py

@@ -17,10 +17,11 @@ from typing import Any, Dict, List, Optional, Tuple
 
 from .battery import _walk
 from .device_local import LocalDeviceClient
+from .wifi import DEVICE_GATEWAY_IP
 
 log = logging.getLogger(__name__)
 
-HOST = "10.100.1.1"
+HOST = DEVICE_GATEWAY_IP
 PORTS: Tuple[int, ...] = (9000, 18000)
 
 #: Reply keys holding watt readings, in priority order.