build: vendor pinned flutter_vless Android runtime (#10)

Replace build-time pub-cache mutation with a repository-owned pinned runtime so reviewed native source is the source compiled into the app.

local_packages/flutter_vless_android-1.1.5/lib/flutter_vless_android.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2024-2026 13FOX Studio / tfox.dev.
+// SPDX-License-Identifier: MIT
+
+import 'package:flutter_vless_platform_interface/flutter_vless_platform_interface.dart';
+
+/// Android implementation of [VlessPlatform] using MethodChannel.
+class FlutterVlessAndroid extends VlessMethodChannelAdapter {
+  /// Registers this class as the platform implementation.
+  /// This is called automatically by Flutter's plugin registry.
+  static void registerWith() {
+    VlessPlatform.instance = FlutterVlessAndroid();
+  }
+}