Add Android Capacitor build system

- Install Capacitor dependencies (@capacitor/cli, @capacitor/core, @capacitor/android, @capacitor/app, @capacitor/status-bar, sharp)
- Create capacitor.config.ts with app configuration
- Update .gitignore to exclude Android build outputs and keystore files
- Generate icon-512.png from logo.svg
- Add scripts for icon generation, APK building, and keystore creation
- Initialize Capacitor Android platform
- Configure build.gradle with signing support
- Generate Android app icons in all required densities
- Add npm scripts: 'icons' and 'build:apk'

.gitignore

@@ -31,3 +31,13 @@ yarn.lock
 .env
 .env.*
 !.env.example
+
+# Android build outputs and sensitive files
+*.aab
+resources/
+android/app/my-upload-key.keystore
+android/key.properties
+android/local.properties
+android/build/
+android/.gradle/
+android/*/build/