Add ASR interim results support in Assistant model and API

- Introduced `asr_interim_enabled` field in the Assistant model to control interim ASR results.
- Updated AssistantBase and AssistantUpdate schemas to include the new field.
- Modified the database schema to add the `asr_interim_enabled` column.
- Enhanced runtime metadata to reflect interim ASR settings.
- Updated API endpoints and tests to validate the new functionality.
- Adjusted documentation to include details about interim ASR results configuration.

engine/app/config.py

@@ -89,6 +89,7 @@ class Settings(BaseSettings):
     )
     asr_api_url: Optional[str] = Field(default=None, description="ASR provider API URL")
     asr_model: Optional[str] = Field(default=None, description="ASR model name")
+    asr_enable_interim: bool = Field(default=False, description="Enable interim transcripts for offline ASR")
     asr_interim_interval_ms: int = Field(default=500, description="Interval for interim ASR results in ms")
     asr_min_audio_ms: int = Field(default=300, description="Minimum audio duration before first ASR result")
     asr_start_min_speech_ms: int = Field(