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/packaged_manifests/debugAndroidTest/processDebugAndroidTestManifest/AndroidManifest.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.usbwebcam.test" >
+
+    <uses-sdk
+        android:minSdkVersion="24"
+        android:targetSdkVersion="34" />
+
+    <instrumentation
+        android:name="android.test.InstrumentationTestRunner"
+        android:functionalTest="false"
+        android:handleProfiling="false"
+        android:label="Tests for com.usbwebcam"
+        android:targetPackage="com.usbwebcam" />
+
+    <application
+        android:debuggable="true"
+        android:extractNativeLibs="false" >
+        <uses-library android:name="android.test.runner" />
+    </application>
+
+</manifest>

android-app/app/build/intermediates/packaged_manifests/debugAndroidTest/processDebugAndroidTestManifest/output-metadata.json

@@ -0,0 +1,18 @@
+{
+  "version": 3,
+  "artifactType": {
+    "type": "PACKAGED_MANIFESTS",
+    "kind": "Directory"
+  },
+  "applicationId": "com.usbwebcam.test",
+  "variantName": "debugAndroidTest",
+  "elements": [
+    {
+      "type": "SINGLE",
+      "filters": [],
+      "attributes": [],
+      "outputFile": "AndroidManifest.xml"
+    }
+  ],
+  "elementType": "File"
+}