Integrate Llamaindex in finesse-backend

[k-allagbe]

Description:

We need to integrate our new index created using llamaindex into our finesse-backend. Use the ailab-llama-search package, which is available for installation via pip in llamaindex-db.

Tasks:

• Integrate ailab-llamaindex-search package.
• Update the backend configuration to use the new index from llamaindex-db.
• Create a new endpoint for it.
• Update tests.
• Update docs.

Acceptance Criteria:

• Searches can be made on the new index with no errors.
• All tests confirm the new index's successful integration.
• Documentation is updated.

[rngadam]

I see that the naming from the description is a bit inconsistent, with llama being used. shall we stick to llamaindex everywhere as that's the name of the product.