feat: Support Langfuse as a tracing backend alternative to Phoenix

[neednlab]

Description

Currently, the agent supports Phoenix for tracing. I would like to add support for Langfuse as an alternative tracing backend. Langfuse is a popular open-source LLM engineering platform that provides detailed tracing and evaluation capabilities.

Proposed Solution

• Add a new configuration option to switch between Phoenix and Langfuse.
• Implement the necessary exporter or integration logic to send traces to Langfuse.

Additional Context

I am willing to work on this.