langfuse integration

[fatihbugrakdogan]

This pull request updates the OpenAI client integration in src/ra/clients/openai.py to optionally use Langfuse's tracing capabilities when available. The code now automatically wraps OpenAI API calls with Langfuse for enhanced observability if the LANGFUSE_SECRET_KEY environment variable is set and the Langfuse package is installed. Otherwise, it defaults to the standard OpenAI client.

Integration with Langfuse tracing:

• Added conditional import and use of Langfuse's OpenAI and AsyncOpenAI clients, enabling automatic tracing when the LANGFUSE_SECRET_KEY environment variable is present.
• Updated client instantiation in both sync and async code paths to prefer Langfuse-wrapped clients if available, falling back to standard OpenAI clients otherwise. [1] [2]