Implement proper asset management and clean up repository

- Add capacitor-assets.config.json for cross-platform asset generation
- Create resources/ directory structure for source assets
- Update .gitignore to exclude generated Android assets and resources
- Remove 30+ generated files from source control
- Add comprehensive asset management documentation
- Add Gradle cache exclusions to .gitignore
- Verify asset generation works with new configuration

Assets are now properly managed: source files in version control,
generated files excluded, and build process handles platform-specific
asset generation automatically. Repository size reduced and history
cleaned up.

.gitignore

@@ -124,3 +124,7 @@ electron/out/
 # - electron/build-packages.sh
 # - electron/live-runner.js
 # - electron/resources/electron-publisher-custom.js
+
+# Gradle cache files
+android/.gradle/file-system.probe
+android/.gradle/caches/