feat: add Android ARMv8 (aarch64) build support

- Initialize Tauri Android project structure (gen/android)
- Fix desktop_dir() unavailability on Android in file_explorer.rs and serial.rs
- Fix minimize/maximize/unmaximize unavailability on Android in window.rs
- Remove updater:default permission from default capabilities (not available on Android)
- Update .gitignore for Android build artifacts
- Successfully builds APK for aarch64-linux-android target

src-tauri/gen/android/settings.gradle

@@ -0,0 +1,3 @@
+include ':app'
+
+apply from: 'tauri.settings.gradle'