Add Jina AI Embeddings Support

[theQuert]

Description

This PR adds support for Jina AI Embeddings as a new retriever option in our RAG system, providing an alternative to existing OpenAI and Gemini embeddings.

Features

• New getJinaRetriever function for Jina AI integration
• Support for "jina-embeddings-v3" model
• Consistent interface with existing retrievers
• Comprehensive error handling and logging

Dependencies

• Requires jinaai package
• Requires JINA_API_KEY environment variable

Checklist

• Code follows project style guidelines
• Error handling implemented