docs: add readme doc with usage and examples

libs/android-docker/README.md

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+# Android Docker
+
+Docker image that runs an Android emulator with CUA Computer Server integration, enabling programmatic control of Android devices via HTTP API.
+
+## Features
+
+- **Android 11 Emulator** - Based on budtmo/docker-android
+- **CUA Computer Server** - HTTP API for automation, file operations, window management
+- **Custom Wallpaper Manager APK** - Programmatically set wallpapers without user interaction
+- **VNC Access** - View and interact with the Android screen via web browser
+
+## What's Inside
+
+- **wallpaper-manager/** - Custom Android APK that uses WallpaperManager API to set wallpapers
+- **entry.sh** - Container startup script that launches emulator and server
+- **Dockerfile** - Production build (installs cua-computer-server from PyPI)
+- **dev.Dockerfile** - Development build (uses local source code)
+
+## Quick Start
+
+### Production Build
+
+```bash
+cd android-docker
+docker build -t cua-android .
+docker run -d -p 6080:6080 -p 8000:8000 \
+  -e EMULATOR_DEVICE="Samsung Galaxy S10" \
+  -e WEB_VNC=true \
+  --device /dev/kvm \
+  --name android-container \
+  cua-android
+```
+
+### Development Build
+
+```bash
+cd ..  # Go to libs/ directory
+docker build -f android-docker/dev.Dockerfile -t cua-android:dev .
+docker run -d -p 6080:6080 -p 8000:8000 \
+  -e EMULATOR_DEVICE="Samsung Galaxy S10" \
+  -e WEB_VNC=true \
+  --device /dev/kvm \
+  --name android-container \
+  cua-android:dev
+```
+
+## Access Points
+
+- **VNC Web UI**: http://localhost:6080
+- **Computer Server API**: http://localhost:8000
+- **API Documentation**: http://localhost:8000/docs
+
+## API Examples
+
+```bash
+# Get screen size
+curl -X POST http://localhost:8000/cmd \
+  -H "Content-Type: application/json" \
+  -d '{"command": "get_screen_size", "params": {}}'
+
+# Set wallpaper (automatically handles permissions)
+curl -X POST http://localhost:8000/cmd \
+  -H "Content-Type: application/json" \
+  -d '{"command": "set_wallpaper", "params": {"path": "/sdcard/image.jpg", "target": "home"}}'
+
+# Launch app
+curl -X POST http://localhost:8000/cmd \
+  -H "Content-Type: application/json" \
+  -d '{"command": "launch", "params": {"app": "com.android.settings"}}'
+```
+
+## Custom Wallpaper Solution
+
+Android doesn't provide native ADB commands for setting wallpapers. We solved this by:
+
+1. **Building a custom APK** (`wallpaper-manager`) that uses Android's WallpaperManager API
+2. **Multi-stage Docker build** - APK is compiled during image build
+3. **Auto-installation** - APK installs automatically on container startup
+4. **Permission handling** - Files are copied to `/data/local/tmp` where all apps have read access
+5. **Seamless integration** - `set_wallpaper()` API handles everything automatically