XFEstudio/gpt4free

Enhance AnyModelProviderMixin to support Perplexity and improve model mapping

- Added Perplexity to the list of providers handled in model mapping. - Simplified model mapping logic for Copilot and CopilotAccount. - Updated handling of fallback models for Perplexity. - Improved clean_name function to standardize model names, including new replacements for gpt-5 and Claude models. - Adjusted model grouping logic to include additional prefixes for Mistral models.