* refactor: use new image output format for agents using DALL-E tools
* refactor: Enhance image fetching with proxy support and adjust logging placement in DALL-E 3 integration
* refactor: Enhance StableDiffusionAPI to support agent-specific return values and display message for generated images
* refactor: Add unit test execution for librechat-mcp in backend review workflow
* refactor: Update environment variable extraction logic, export from serpate module to avoid circular refs, and remove deprecated tests
* refactor: Add unit tests for environment variable extraction and enhance StdioOptionsSchema to process env variables
