fix: langfuse talk to model

[chloedia]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context.

Checklist before requesting a review

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• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented hard-to-understand areas
• I have ideally added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged

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[AmineDiro]

This is a global object cant we put it in some class?

[chloedia]

Like this ?

Suggested change

	langfuse_handler = CallbackHandler()
	langfuse_service = LangfuseService()
	langfuse_handler = langfuse_service.get_handler()

With a class defined in utils :

class LangfuseService:
    def __init__(self):
        self.langfuse_handler = CallbackHandler()

    def get_handler(self):
        return self.langfuse_handler