Share core logic between Kotlin/JVM/Android and Node.js/JavaScript

[litlfred]

Summary

Refactor or migrate core logic to enable sharing between Kotlin/JVM/Android and Node.js/JavaScript environments. This will allow for a single source of truth for business logic, improving maintainability and fostering cross-platform support.

Details

• Identify core business logic in the current TypeScript codebase.
• Migrate or rewrite this logic in a Kotlin/JS module that can be compiled to JavaScript as well as used natively in JVM/Android projects.
• Set up Kotlin/JS build process in the repository (using Gradle).
• Update Node.js/JavaScript code to consume the compiled Kotlin/JS output.
• Document the new build steps and usage for both Kotlin and JS downstream consumers.

Acceptance Criteria

• Core logic is implemented in Kotlin and can be consumed from both JVM/Android and Node.js/JS (as a compiled artifact).
• Clear documentation for adding/updating shared logic and for consuming it in both platforms.
• CI updated to build and test both Kotlin and JS artifacts.

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This issue is to enable true cross-platform logic sharing and reduce code duplication for future maintenance and feature development.