feat(android): 添加 CH934X USB 转串口芯片支持

- 在 AndroidManifest.xml 中添加 USB Host 权限声明
- 集成 CH934X Android SDK 并通过反射调用原生功能
- 实现设备查找、串口读写、GPIO 和 Modem 控制功能
- 添加异常回调机制处理设备拔出等情况
- 提供 Stream 数据流支持实时串口数据监听
- 完善单元测试覆盖所有核心功能模块

example/android/app/src/main/AndroidManifest.xml

@@ -1,4 +1,9 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- 文档 2:USB Host 能力声明,使用 CH934X 转接设备时必须开启。 -->
+    <uses-feature
+        android:name="android.hardware.usb.host"
+        android:required="true" />
+
     <application
         android:label="ch934x_serial_example"
         android:name="${applicationName}"
@@ -12,10 +17,6 @@
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
             android:windowSoftInputMode="adjustResize">
-            <!-- Specifies an Android theme to apply to this Activity as soon as
-                 the Android process has started. This theme is visible to the user
-                 while the Flutter UI initializes. After that, this theme continues
-                 to determine the Window background behind the Flutter UI. -->
             <meta-data
               android:name="io.flutter.embedding.android.NormalTheme"
               android:resource="@style/NormalTheme"
@@ -25,17 +26,10 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
-        <!-- Don't delete the meta-data below.
-             This is used by the Flutter tool to generate GeneratedPluginRegistrant.java -->
         <meta-data
             android:name="flutterEmbedding"
             android:value="2" />
     </application>
-    <!-- Required to query activities that can process text, see:
-         https://developer.android.com/training/package-visibility and
-         https://developer.android.com/reference/android/content/Intent#ACTION_PROCESS_TEXT.
-
-         In particular, this is used by the Flutter engine in io.flutter.plugin.text.ProcessTextPlugin. -->
     <queries>
         <intent>
             <action android:name="android.intent.action.PROCESS_TEXT"/>