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.

docs/content/customization/asr.md

@@ -13,6 +13,7 @@
 |---|---|
 | ASR 引擎 | 选择语音识别服务提供商 |
 | 模型 | 识别模型名称 |
+| `enable_interim` | 是否开启离线 ASR 中间结果（默认 `false`，仅离线模式生效） |
 | 语言 | 中文/英文/多语言 |
 | 热词 | 提升特定词汇识别准确率 |
 | 标点与规范化 | 是否自动补全标点、文本规范化 |