feat: 添加 USB 摄像头连接功能

- 新增 Android USB 摄像头 APP (MJPEG 服务器)
- 电脑端支持 ADB 端口转发连接
- 修复 .gitignore 忽略 Android 文件

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android-app/app/build/intermediates/merged_manifest/debug/processDebugMainManifest/AndroidManifest.xml

@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.usbwebcam"
+    android:versionCode="1"
+    android:versionName="1.0" >
+
+    <uses-sdk
+        android:minSdkVersion="24"
+        android:targetSdkVersion="34" />
+
+    <uses-feature android:name="android.hardware.camera.any" />
+
+    <uses-permission android:name="android.permission.CAMERA" />
+    <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+
+    <permission
+        android:name="com.usbwebcam.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION"
+        android:protectionLevel="signature" />
+
+    <uses-permission android:name="com.usbwebcam.DYNAMIC_RECEIVER_NOT_EXPORTED_PERMISSION" />
+
+    <application
+        android:allowBackup="true"
+        android:appComponentFactory="androidx.core.app.CoreComponentFactory"
+        android:debuggable="true"
+        android:extractNativeLibs="false"
+        android:label="USB摄像头"
+        android:testOnly="true"
+        android:theme="@style/Theme.AppCompat.NoActionBar" >
+        <activity
+            android:name="com.usbwebcam.MainActivity"
+            android:exported="true"
+            android:keepScreenOn="true"
+            android:screenOrientation="landscape" >
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+
+        <provider
+            android:name="androidx.startup.InitializationProvider"
+            android:authorities="com.usbwebcam.androidx-startup"
+            android:exported="false" >
+            <meta-data
+                android:name="androidx.emoji2.text.EmojiCompatInitializer"
+                android:value="androidx.startup" />
+            <meta-data
+                android:name="androidx.lifecycle.ProcessLifecycleInitializer"
+                android:value="androidx.startup" />
+        </provider>
+    </application>
+
+</manifest>