Track battery percentage history; skip poll write when value unchanged

ha_poller.py

@@ -1,5 +1,6 @@
 import logging
 import threading
+from datetime import datetime
 
 logger = logging.getLogger(__name__)
 
@@ -36,7 +37,7 @@ class HaPoller:
             self._poll_once()
 
     def _poll_once(self):
-        from models import Battery, Device  # local import avoids circular-import risk
+        from models import Battery, BatteryPctLog, Device  # local import avoids circular-import risk
 
         session = self._Session()
         try:
@@ -49,8 +50,14 @@ class HaPoller:
                 pct = self._client.get_state(device.ha_entity_id)
                 if pct is not None:
                     for battery in device.batteries:
-                        if battery.status == "installed":
+                        if battery.status == "installed" and battery.battery_percentage != pct:
                             battery.battery_percentage = pct
+                            session.add(BatteryPctLog(
+                                battery_id=battery.id,
+                                percentage=pct,
+                                recorded_at=datetime.utcnow().strftime("%Y-%m-%d %H:%M:%S"),
+                                source="poll",
+                            ))
             session.commit()
             logger.debug("HA poll complete (%d devices checked)", len(devices))
         except Exception as exc: