refactor(android)!: restructure to standard Capacitor plugin layout

Restructure Android project from nested module layout to standard
Capacitor plugin structure following community conventions.

Structure Changes:
- Move plugin code from android/plugin/ to android/src/main/java/
- Move test app from android/app/ to test-apps/android-test-app/app/
- Remove nested android/plugin module structure
- Remove nested android/app test app structure

Build Infrastructure:
- Add Gradle wrapper files (gradlew, gradlew.bat, gradle/wrapper/)
- Transform android/build.gradle from root project to library module
- Update android/settings.gradle for standalone plugin builds
- Add android/gradle.properties with AndroidX configuration
- Add android/consumer-rules.pro for ProGuard rules

Configuration Updates:
- Add prepare script to package.json for automatic builds on npm install
- Update package.json version to 1.0.1
- Update android/build.gradle to properly resolve Capacitor dependencies
- Update test-apps/android-test-app/settings.gradle with correct paths
- Remove android/variables.gradle (hardcode values in build.gradle)

Documentation:
- Update BUILDING.md with new structure and build process
- Update INTEGRATION_GUIDE.md to reflect standard structure
- Update README.md to remove path fix warnings
- Add test-apps/BUILD_PROCESS.md documenting test app build flows

Test App Configuration:
- Fix android-test-app to correctly reference plugin and Capacitor
- Remove capacitor-cordova-android-plugins dependency (not needed)
- Update capacitor.settings.gradle path verification in fix script

BREAKING CHANGE: Plugin now uses standard Capacitor Android structure.
Consuming apps must update their capacitor.settings.gradle to reference
android/ instead of android/plugin/. This is automatically handled by
Capacitor CLI for apps using standard plugin installation.

android/.gitignore

@@ -16,13 +16,17 @@
 bin/
 gen/
 out/
-#  Uncomment the following line in case you need and you don't have the release build type files in your app
-# release/
 
 # Gradle files
 .gradle/
 build/
 
+# Keep gradle wrapper files - they're needed for builds
+!gradle/wrapper/gradle-wrapper.jar
+!gradle/wrapper/gradle-wrapper.properties
+!gradlew
+!gradlew.bat
+
 # Local configuration file (sdk path, etc)
 local.properties
 
@@ -38,19 +42,9 @@ proguard/
 # Android Studio captures folder
 captures/
 
-# IntelliJ
+# IntelliJ / Android Studio
 *.iml
-.idea/workspace.xml
-.idea/tasks.xml
-.idea/gradle.xml
-.idea/assetWizardSettings.xml
-.idea/dictionaries
-.idea/libraries
-# Android Studio 3 in .gitignore file.
-.idea/caches
-.idea/modules.xml
-# Comment next line if keeping position of elements in Navigation Editor is relevant for you
-.idea/navEditor.xml
+.idea/
 
 # Keystore files
 # Uncomment the following lines if you do not want to check your keystore files in.
@@ -64,38 +58,6 @@ captures/
 # Google Services (e.g. APIs or Firebase)
 # google-services.json
 
-# Freeline
-freeline.py
-freeline/
-freeline_project_description.json
-
-# fastlane
-fastlane/report.xml
-fastlane/Preview.html
-fastlane/screenshots
-fastlane/test_output
-fastlane/readme.md
-
-# Version control
-vcs.xml
-
-# lint
-lint/intermediates/
-lint/generated/
-lint/outputs/
-lint/tmp/
-# lint/reports/
-
 # Android Profiling
 *.hprof
 
-# Cordova plugins for Capacitor
-capacitor-cordova-android-plugins
-
-# Copied web assets
-app/src/main/assets/public
-
-# Generated Config files
-app/src/main/assets/capacitor.config.json
-app/src/main/assets/capacitor.plugins.json
-app/src/main/res/xml/config.xml