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.

lib/servicios/servicio_dispositivo_audio.dart

@@ -55,6 +55,19 @@ abstract class ServicioDispositivoAudio {
   /// denied.
   Future<bool> solicitarPermisoBluetooth();
 
+  /// Returns the names the system remembers for every PAIRED Bluetooth device,
+  /// keyed by uppercase MAC.
+  ///
+  /// `AudioDeviceInfo.productName` only exists for devices the platform is
+  /// enumerating right now, i.e. currently connected ones, so a paired device
+  /// sitting in a drawer can never report its own name. The bond list is the
+  /// authoritative source that survives disconnection.
+  ///
+  /// Returns an empty map when the answer is unavailable rather than throwing:
+  /// `BLUETOOTH_CONNECT` may be denied, and a missing name must degrade to the
+  /// id fallback, never break device resolution.
+  Future<Map<String, String>> obtenerNombresEmparejados() async => const {};
+
   /// Cancels the device-change subscription and releases resources.
   Future<void> dispose();
 }
@@ -130,6 +143,22 @@ class ServicioDispositivoAudioReal extends ServicioDispositivoAudio {
     return granted ?? false;
   }
 
+  @override
+  Future<Map<String, String>> obtenerNombresEmparejados() async {
+    try {
+      final raw = await _methodChannel.invokeMethod<Map>('getBondedDeviceNames');
+      if (raw == null) return const {};
+      return {
+        for (final entry in raw.entries)
+          if (entry.key is String && entry.value is String)
+            (entry.key as String).toUpperCase(): entry.value as String,
+      };
+    } catch (_) {
+      // Denied permission or no adapter: fall back to the id, never throw.
+      return const {};
+    }
+  }
+
   @override
   Future<void> dispose() async {
     await _eventSub?.cancel();