Kaapi code: Explore code structure better than monolith

[nishika26]

Describe the current behavior
Kaapi's backend currently follows a monolithic architecture where all functionality (authentication, collections, LLM providers, document processing, evaluations, fine-tuning, etc.) exists within a single codebase and runs as a single application. While this approach has worked well for initial development, it presents its own limitations.

Describe the enhancement you'd like
Conduct a comprehensive exploration and evaluation of architectural patterns that could improve upon the current monolithic structure.