feat: 添加 Android USB 摄像头 APP 源代码

- 源代码文件: MainActivity, CameraHelper, MjpegServer
- 布局文件: activity_main.xml
- 优化 .gitignore 只忽略构建产物

.gitignore

@@ -1,21 +1,22 @@
+# Data
 data/input/*
 !data/input/.gitkeep
 data/output/*
 !data/output/.gitkeep
+
+# Python
 __pycache__/
 *.pyc
 .DS_Store
 .venv/
 venv/
 
-# Android
-android-app/
-*.apk
-*.ap_
-*.aab
+# Android - 源代码保留，忽略构建产物
 android-app/app/build/
-android-app/.idea/
 android-app/.gradle/
+android-app/.idea/
 android-app/local.properties
 android-app/captures/
-
+android-app/*.apk
+android-app/*.aab
+android-app/.gradle/

android-app/.idea/workspace.xml

@@ -10,8 +10,7 @@
   </component>
   <component name="ChangeListManager">
     <list default="true" id="129a9e13-1934-4081-883b-3b7d2dedc07d" name="Changes" comment="">
-      <change afterPath="$PROJECT_DIR$/gradle/wrapper/gradle-wrapper.properties" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/../src/desktop.py" beforeDir="false" afterPath="$PROJECT_DIR$/../src/desktop.py" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/../.gitignore" beforeDir="false" afterPath="$PROJECT_DIR$/../.gitignore" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />