Use LAA MAC bit to auto-detect phones/wearables for occupancy

Modern phones use private/random MACs (iOS 14+, Android 10+) which
always have the locally-administered bit set (bit 1 of first octet).
TVs, gateways, and smart home devices use globally-assigned OUI MACs
where this bit is clear.

No configuration needed — any LAA MAC counts toward occupancy.
Explicit device_labels/personal_devices still work as fallback.

net_alerter/net_alerter.py

@@ -901,11 +901,18 @@ def _update_occupancy_state_unlocked() -> None:
     """
     global location_occupancy
 
-    # Count only explicitly configured personal devices (phones/wearables in device_labels or personal_devices)
+    # Detect phones/wearables via LAA MAC (locally-administered bit set in first octet).
-    # Ignores all other devices — TVs, smart home, unknown equipment, etc.
+    # iOS 14+, Android 10+ all use private/random MACs — this bit is always set.
+    # TVs, gateways, smart home devices use globally-assigned OUI MACs (bit clear).
+    # Explicit device_labels / personal_devices also qualify (older phones, pre-config).
     def _is_personal(mac: str) -> bool:
         n = _normalize_mac(mac)
-        return n in device_labels or n in personal_devices
+        if n in device_labels or n in personal_devices:
+            return True
+        try:
+            return bool(int(n[:2], 16) & 0x02)  # locally-administered bit
+        except ValueError:
+            return False
 
     active_enrolled_count = 0
     for mac, dev in known_devices.items():