Add class-level _settings type annotations to all service classes for better editor support.

Standardize all STT, TTS, and LLM service classes to declare `_settings` with the narrowed Settings type as a class-level annotation. This gives editors and type checkers the specific type when hovering or autocompleting on `self._settings` in each service and its subclasses. Inline `self._settings: Type = ...` assignments are replaced with plain `self._settings = ...`.

src/pipecat/services/gradium/stt.py

@@ -86,6 +86,8 @@ class GradiumSTTService(WebsocketSTTService):
     for audio processing and connection management.
     """
 
+    _settings: GradiumSTTSettings
+
     class InputParams(BaseModel):
         """Configuration parameters for Gradium STT API.
 
@@ -145,7 +147,7 @@ class GradiumSTTService(WebsocketSTTService):
 
         params = params or GradiumSTTService.InputParams()
 
-        self._settings: GradiumSTTSettings = GradiumSTTSettings(
+        self._settings = GradiumSTTSettings(
             language=params.language,
             delay_in_frames=params.delay_in_frames if params.delay_in_frames else NOT_GIVEN,
         )