Add Settings class attribute alias to all service classes

Add a `Settings` class-level alias on every STT, LLM, TTS, image,
vision, and video service class pointing to its settings dataclass.
This lets developers discover the right settings class via the service
class itself (e.g. `GoogleSTTService.Settings(...)`) without needing
to know or import the separate settings class name.

src/pipecat/services/cerebras/llm.py

@@ -31,6 +31,7 @@ class CerebrasLLMService(OpenAILLMService):
     maintaining full compatibility with OpenAI's interface and functionality.
     """
 
+    Settings = CerebrasLLMSettings
     _settings: CerebrasLLMSettings
 
     def __init__(