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/estado/estado_ecualizador.dart

@@ -176,6 +176,7 @@ class EstadoEcualizador extends ChangeNotifier {
 
       // Seed current device immediately so presets resolve before first event.
       if (_eqMultiDeviceEnabled) {
+        await _sembrarNombresEmparejados();
         await _sembrarDispositivoActual();
       }
     } catch (_) {
@@ -190,6 +191,30 @@ class EstadoEcualizador extends ChangeNotifier {
     }
   }
 
+  /// Fills [_nombresPlataforma] from the system's paired-device list.
+  ///
+  /// A Bluetooth device only reports its own name while it is connected, so
+  /// without this a device the user never renamed shows its raw id whenever it
+  /// is switched off — which is most of the time. The bond list is the system's
+  /// own record and survives disconnection.
+  ///
+  /// Seeded BEFORE [_sembrarDispositivoActual] so a live enumeration name (the
+  /// fresher of the two) overwrites the paired one rather than the reverse.
+  /// Never throws: a device with no resolvable name just falls back to its id.
+  Future<void> _sembrarNombresEmparejados() async {
+    final svc = _dispositivoAudio;
+    if (svc == null) return;
+    try {
+      final emparejados = await svc.obtenerNombresEmparejados();
+      for (final entry in emparejados.entries) {
+        if (entry.value.isEmpty) continue;
+        _nombresPlataforma['bt_a2dp:${entry.key}'] = entry.value;
+      }
+    } catch (_) {
+      // Permission denied or no adapter: keep whatever names we already have.
+    }
+  }
+
   /// Queries the current device and seeds [_dispositivoActualId] without
   /// waiting for a stream event. Falls back to `'builtin_speaker'` on error.
   Future<void> _sembrarDispositivoActual() async {
@@ -232,6 +257,10 @@ class EstadoEcualizador extends ChangeNotifier {
     } catch (_) {
       // A failed resubscribe must never block the fresh-query re-seed below.
     }
+    // Re-read the bond list too: the user may have paired or renamed a device
+    // in system settings since the app started, and this runs right as the
+    // device list becomes visible.
+    await _sembrarNombresEmparejados();
     await _sembrarDispositivoActual();
   }