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/tests/test_asr_factory_modes.py

@@ -32,6 +32,7 @@ def test_create_asr_service_openai_compatible_returns_offline_provider():
     )
     assert isinstance(service, OpenAICompatibleASRService)
     assert service.mode == "offline"
+    assert service.enable_interim is False
 
 
 def test_create_asr_service_fallback_buffered_for_unsupported_provider():