feat(eq): add per-device equalizer with 4-level preset resolution

Introduce multi-device EQ support allowing each audio output device
(built-in speaker, wired, USB, individual Bluetooth by MAC) to have
its own equalizer preset, combined with existing per-station presets
for a full station×device matrix.

- Add DispositivoAudio model and ServicioDispositivoAudio interface
- Add Android platform channel (AudioDeviceCallback) for device detection
- Add iOS AudioDevicesPlugin (AVAudioSession route tracking)
- Extend ServicioEcualizador with device and matrix persistence keys
- Implement 4-level resolution: matrix > station > device > global
- Add advanced EQ settings section with feature toggle (off by default)
- Extend export/import to v3 with backward compatibility
- 184 tests passing, zero analyzer issues

lib/l10n/gen/app_localizations.dart

@@ -2269,6 +2269,42 @@ abstract class AppLocalizations {
   /// In es, this message translates to:
   /// **'https://stream.example.com:8000/radio'**
   String get streamUrlHint;
+
+  /// No description provided for @advancedEqSectionTitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Opciones avanzadas de ecualización'**
+  String get advancedEqSectionTitle;
+
+  /// No description provided for @advancedEqEnableToggle.
+  ///
+  /// In es, this message translates to:
+  /// **'Activar EQ por dispositivo'**
+  String get advancedEqEnableToggle;
+
+  /// No description provided for @advancedEqEnableToggleSubtitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Aplica automáticamente un preset de EQ distinto al cambiar la salida de audio.'**
+  String get advancedEqEnableToggleSubtitle;
+
+  /// No description provided for @advancedEqKnownDevicesTitle.
+  ///
+  /// In es, this message translates to:
+  /// **'Dispositivos de audio conocidos'**
+  String get advancedEqKnownDevicesTitle;
+
+  /// No description provided for @advancedEqKnownDevicesEmpty.
+  ///
+  /// In es, this message translates to:
+  /// **'No hay dispositivos registrados. Conectá uno para empezar.'**
+  String get advancedEqKnownDevicesEmpty;
+
+  /// No description provided for @advancedEqDevicePresetLabel.
+  ///
+  /// In es, this message translates to:
+  /// **'Preset: {presetName}'**
+  String advancedEqDevicePresetLabel(Object presetName);
 }
 
 class _AppLocalizationsDelegate