docs: add Android physical device deployment guide

Add comprehensive guide for building and testing TimeSafari on physical
Android devices, covering device setup, USB debugging, network
configuration for local development servers, and troubleshooting.

- Create doc/android-physical-device-guide.md with full instructions
- Update BUILDING.md to reference the new guide in two places

BUILDING.md

@@ -1301,7 +1301,8 @@ npm run build:android:test:run   # test env build, install, launch
 
 ##### Reference
 
-- Full troubleshooting and options: [doc/android-emulator-deployment-guide.md](doc/android-emulator-deployment-guide.md)
+- Emulator troubleshooting and options: [doc/android-emulator-deployment-guide.md](doc/android-emulator-deployment-guide.md)
+- **Physical device testing**: [doc/android-physical-device-guide.md](doc/android-physical-device-guide.md)
 
 #### Android Build Commands
 
@@ -1811,6 +1812,8 @@ npm run build:android:assets
 - [Electron Build Patterns](docs/electron-build-patterns.md)
 - [iOS Build Scripts](docs/ios-build-scripts.md)
 - [Android Build Scripts](docs/android-build-scripts.md)
+- [Android Physical Device Guide](doc/android-physical-device-guide.md)
+- [Android Emulator Deployment Guide](doc/android-emulator-deployment-guide.md)
 - [Web Build Scripts](docs/web-build-scripts.md)
 - [Build Troubleshooting](docs/build-troubleshooting.md)