refactor(native-player): share player helpers

lib/providers/theme_provider.dart

@@ -66,7 +66,7 @@ class ThemeProvider extends ChangeNotifier {
     }
   }
 
-  static const _themeChannel = MethodChannel('app.plezy/theme');
+  static const _themeChannel = MethodChannel('com.plezy/theme');
 
   Future<void> setThemeMode(settings.ThemeMode mode) async {
     if (_themeMode != mode) {

lib/services/external_player_service.dart

@@ -11,7 +11,7 @@ import '../i18n/strings.g.dart';
 import 'plex_client.dart';
 import 'settings_service.dart';
 
-const _externalPlayerChannel = MethodChannel('app.plezy/external_player');
+const _externalPlayerChannel = MethodChannel('com.plezy/external_player');
 
 class ExternalPlayerService {
   /// Launch an external player with either a pre-resolved [videoUrl] (e.g. local

lib/services/pip_service.dart

@@ -5,7 +5,7 @@ import 'package:flutter/services.dart';
 import 'package:plezy/i18n/strings.g.dart';
 
 class PipService {
-  static const MethodChannel _channel = MethodChannel('app.plezy/pip');
+  static const MethodChannel _channel = MethodChannel('com.plezy/pip');
 
   /// PiP is only implemented natively on Android, iOS, and macOS.
   static bool get _isAvailable => Platform.isAndroid || Platform.isIOS || Platform.isMacOS;

lib/services/watch_next_service.dart

@@ -9,7 +9,7 @@ import 'settings_service.dart' show EpisodePosterMode;
 
 /// Service for syncing Plex "On Deck" content to Android TV's Watch Next row.
 class WatchNextService {
-  static const MethodChannel _channel = MethodChannel('app.plezy/watch_next');
+  static const MethodChannel _channel = MethodChannel('com.plezy/watch_next');
 
   static final WatchNextService _instance = WatchNextService._internal();
   factory WatchNextService() => _instance;