feat(eq): name Bluetooth devices from the system pairing list

A Bluetooth device only reports its own name through
AudioDeviceInfo.productName while it is enumerated as an active output, i.e.
while it is connected. Paired-but-switched-off devices therefore had no name
to fall back on, and the platform-name cache is in-memory only by design
(bt-device-identity ADR-4), so it self-heals per session ONLY for whatever
happens to be connected. Every other device showed its raw id.

Android already knows those names: BluetoothAdapter.getBondedDevices() lists
every pairing with its name and MAC, connected or not, and nothing in this
app was asking. Read it and seed the platform-name cache from it, keyed
bt_a2dp:<uppercase MAC> to match the ids the audio layer emits.

Seeded BEFORE the active-device query so a live enumeration name, being the
fresher of the two, still wins; a user's custom name outranks both. Re-read
on refrescarDispositivoActual so pairing or renaming a device in system
settings shows up as soon as the list becomes visible.

Reading the bond list is gated by BLUETOOTH_CONNECT from API 31 and by the
legacy BLUETOOTH permission below it, so declare the latter with
maxSdkVersion 30. It is a normal permission: granted at install, no runtime
prompt, no new friction. When the answer is unavailable — permission denied,
no adapter, Bluetooth off — both layers return an empty map rather than
throwing, and the row degrades to the id exactly as before.

Does not help rows persisted under a bt_a2dp:name: placeholder id: those
never had a MAC to match against.

test/helpers/fakes.dart

@@ -465,6 +465,11 @@ class FakeServicioDispositivoAudioThrows extends ServicioDispositivoAudio {
     throw Exception('Platform channel error: device unavailable');
   }
 
+  @override
+  Future<Map<String, String>> obtenerNombresEmparejados() async {
+    throw Exception('Platform channel error: bonded devices unavailable');
+  }
+
   @override
   Future<void> resubscribir() async {
     resubscribirLlamadas++;
@@ -485,7 +490,17 @@ class FakeServicioDispositivoAudioThrows extends ServicioDispositivoAudio {
 /// Use [emitirDispositivo] to push device change events without needing
 /// a real platform channel.
 class FakeServicioDispositivoAudio extends ServicioDispositivoAudio {
-  FakeServicioDispositivoAudio({this.permisoBluetoothConcedido = true});
+  FakeServicioDispositivoAudio({
+    this.permisoBluetoothConcedido = true,
+    this.nombresEmparejados = const {},
+  });
+
+  /// MAC → name entries the system would report for PAIRED devices.
+  final Map<String, String> nombresEmparejados;
+
+  @override
+  Future<Map<String, String>> obtenerNombresEmparejados() async =>
+      nombresEmparejados;
 
   /// Value returned by [solicitarPermisoBluetooth] (bt-device-identity
   /// Phase 2/4 testing strategy — defaults to granted so existing tests