fix: follow Bluetooth adapters that change their hci index

[dingausmwald]

Fixes #830

Problem

When the kernel resets a Bluetooth dongle, the dongle can come back under a different hci index. This happens for example after a command tx timeout on a Realtek RTL8761BU. After that, BLE monitor keeps using the old index and never recovers until Home Assistant Core is restarted. Reloading the integration does not help.

The log from a Raspberry Pi 4 on 14.2.0, where the dongle 00:E0:42:A7:E9:03 moved from hci2 to hci0:

kernel: Bluetooth: hci2: command tx timeout
kernel: Bluetooth: hci2: Resetting usb device.
kernel: Bluetooth: hci0: RTL: fw version 0xdfc6d922
...
ERROR (Thread-3) [custom_components.ble_monitor] HCIdump thread: OS error (hci2): [Errno 19] error while attempting to bind on interface 2: No such device
ERROR (Thread-3) [custom_components.ble_monitor] HCIdump thread: Trying to power cycle Bluetooth adapter hci2 00:E0:42:A7:E9:03, will try to use it next scan period.
ERROR (Thread-3) [custom_components.ble_monitor.bt_helpers] hci2 seems not to exist (anymore), check BT interface mac address in your settings. Available adapters: {0: '00:E0:42:A7:E9:03', 1: 'E4:5F:01:74:E1:FF'}

The last three lines repeat every minute. In this case they ran for 8.5 hours until Core was restarted by hand.

Cause

The configured MAC address is resolved to an hci index only once, in async_setup_entry, and the lookup table it uses (BT_INTERFACES) is built once when the module is imported. After that, HCIdump and reset_bluetooth() only work with the stored index, even though the MAC address is known.

Fix

• At the start of each scan period, HCIdump looks up the current index of each configured adapter by its MAC address and uses that index. When an index changes, a warning is logged. If an adapter is currently missing, it keeps its old index, so the existing power-cycle recovery behaves as before.
• The power-cycle log message no longer uses BT_INTERFACES[iface]. That lookup raised a KeyError in the HCIdump thread when the new index was not present at import time.
• bt_helpers.hci_get_all_mac() returns all available adapters. hci_get_mac() now uses it and behaves as before.

If hci_interface is configured in YAML and no MAC address is known for it, nothing changes.

Tests

• New test/test_hcidump_interfaces.py covers a renumbered adapter, an unchanged adapter, a missing adapter, two adapters swapping indexes, disabled Bluetooth, an index without a known MAC address, and hci_get_mac/hci_get_all_mac.
• The full test suite passes with pytest on Python 3.14, using requirements_test.txt.

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