Add optional Home Assistant integration for battery percentage tracking

ha_poller.py

@@ -0,0 +1,60 @@
+import logging
+import threading
+
+logger = logging.getLogger(__name__)
+
+
+class HaPoller:
+    """Background daemon thread that periodically polls Home Assistant
+    for battery percentages and updates installed batteries in the DB.
+
+    Lifecycle:
+        poller = HaPoller(ha_client, session_factory, interval_seconds)
+        poller.start()   # called once from create_app
+        poller.stop()    # not normally needed; daemon thread exits with the process
+    """
+
+    def __init__(self, ha_client, session_factory, interval: int):
+        self._client = ha_client
+        self._Session = session_factory
+        self._interval = interval
+        self._stop = threading.Event()
+        self._thread = threading.Thread(
+            target=self._run, name="ha-poller", daemon=True
+        )
+
+    def start(self):
+        self._thread.start()
+        logger.info("HA poller started (interval=%ds)", self._interval)
+
+    def stop(self):
+        self._stop.set()
+
+    def _run(self):
+        # Wait first so startup DB activity settles before the first poll
+        while not self._stop.wait(self._interval):
+            self._poll_once()
+
+    def _poll_once(self):
+        from models import Battery, Device  # local import avoids circular-import risk
+
+        session = self._Session()
+        try:
+            devices = (
+                session.query(Device)
+                .filter(Device.ha_entity_id.isnot(None))
+                .all()
+            )
+            for device in devices:
+                pct = self._client.get_state(device.ha_entity_id)
+                if pct is not None:
+                    for battery in device.batteries:
+                        if battery.status == "installed":
+                            battery.battery_percentage = pct
+            session.commit()
+            logger.debug("HA poll complete (%d devices checked)", len(devices))
+        except Exception as exc:
+            session.rollback()
+            logger.warning("HA poll failed: %s", exc)
+        finally:
+            session.close()