Fix Language enum conversion at init time in base TTS/STT services

When a Language enum (e.g. Language.ES) is passed via
settings=Service.Settings(language=Language.ES), it gets stored as-is
without conversion to the service-specific code. The base
_update_settings() handles this for runtime updates, but at init time
apply_update() copies the raw enum. This causes API errors because
services send the unconverted enum value.

Add language conversion in TTSService.__init__ and STTService.__init__
after super().__init__(), using the subclass language_to_service_language()
via normal method resolution.

src/pipecat/services/stt_service.py

@@ -120,6 +120,15 @@ class STTService(AIService):
             or STTSettings(),
             **kwargs,
         )
+
+        # Convert Language enum to service-specific format at init time.
+        # Runtime updates are handled by _update_settings(), but init-time
+        # settings bypass that path and need explicit conversion.
+        if isinstance(self._settings.language, Language):
+            converted = self.language_to_service_language(self._settings.language)
+            if converted is not None:
+                self._settings.language = converted
+
         self._audio_passthrough = audio_passthrough
         self._init_sample_rate = sample_rate
         self._sample_rate = 0

src/pipecat/services/tts_service.py

@@ -245,6 +245,14 @@ class TTSService(AIService):
             **kwargs,
         )
 
+        # Convert Language enum to service-specific format at init time.
+        # Runtime updates are handled by _update_settings(), but init-time
+        # settings bypass that path and need explicit conversion.
+        if isinstance(self._settings.language, Language):
+            converted = self.language_to_service_language(self._settings.language)
+            if converted is not None:
+                self._settings.language = converted
+
         # Resolve text_aggregation_mode from the new param or deprecated aggregate_sentences
         if aggregate_sentences is not None:
             import warnings