- Register SiliconFlow in transcription registry with default model FunAudioLLM/SenseVoiceSmall and alias 'silicon' - Reuse existing OpenAITranscriptionProvider adapter (Whisper-compatible) - Add generic key/base resolution: fallback to registry env_key and default_api_base when provider config is absent - Add tests for registry entry, alias, adapter, default model, and config resolution with env var fallback