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/.gitignore

@@ -0,0 +1,20 @@
+*.iml
+.gradle
+/local.properties
+/.idea/caches
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+/.idea/navEditor.xml
+/.idea/assetWizardSettings.xml
+.DS_Store
+build
+/captures
+.externalNativeBuild
+.cxx
+local.properties
+key.properties
+keystore.properties
+
+/.tauri
+/tauri.settings.gradle