fix: use BLE adapter address for RAPT Pill device identity

The MAC bytes inside the RAPT payload change per broadcast and are
not the device's stable identity. Use device.address from Bleak
(the BLE adapter address) instead, so only one device appears.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: machug

backend/scanner.py

@@ -216,17 +216,19 @@ def _detection_callback(self, device, advertisement_data):
                 temp_c = temp_raw / 128.0 - 273.15
                 sg = gravity_raw / 1000.0
                 battery_pct = battery_raw / 256.0
-                mac_str = ":".join(f"{b:02X}" for b in mac_bytes)
+                # Use the BLE adapter address as stable identifier, not the
+                # payload MAC bytes which change per broadcast
+                ble_addr = device.address.upper()
 
                 self._latest_rapt_reading = RAPTPillReading(
-                    mac=mac_str,
+                    mac=ble_addr,
                     temp_c=round(temp_c, 2),
                     sg=round(sg, 4),
                     battery_percent=round(battery_pct, 1),
                     rssi=advertisement_data.rssi,
                     timestamp=datetime.now(timezone.utc),
                 )
-                print(f"BLE: Detected RAPT Pill ({mac_str}) - {temp_c:.1f}C, SG {sg:.4f}, Battery {battery_pct:.0f}%")
+                print(f"BLE: Detected RAPT Pill ({ble_addr}) - {temp_c:.1f}C, SG {sg:.4f}, Battery {battery_pct:.0f}%")
             except Exception as e:
                 logger.debug("Error parsing RAPT Pill packet: %s", e)
             return