perf: add auto voice emotion for minimax tts

[Soulter]

closes: #4193

Modifications / 改动点

• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

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Checklist / 检查清单

• 😊 如果 PR 中有新加入的功能，已经通过 Issue / 邮件等方式和作者讨论过。/ If there are new features added in the PR, I have discussed it with the authors through issues/emails, etc.
• 👀 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。/ My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
• 🤓 我确保没有引入新依赖库，或者引入了新依赖库的同时将其添加到了 requirements.txt 和 pyproject.toml 文件相应位置。/ I have ensured that no new dependencies are introduced, OR if new dependencies are introduced, they have been added to the appropriate locations in requirements.txt and pyproject.toml.
• 😮 我的更改没有引入恶意代码。/ My changes do not introduce malicious code.

Summary by Sourcery

更新 Minimax TTS 语音情感处理，以支持自动情感选择，并使默认配置与新选项保持一致。

新功能：

• 为 Minimax TTS 添加对 auto 情感模式的支持，使服务可以根据文本内容自动选择情感。

改进：

• 扩展 Minimax TTS 可配置的情感选项，并更新默认设置以使用自动情感选择。

Original summary in English

Summary by Sourcery

Update Minimax TTS voice emotion handling to support automatic emotion selection and align default configuration with the new option.

New Features:

• Add support for an auto emotion mode in Minimax TTS that lets the service choose emotion based on text content.

Enhancements:

• Expand the configurable emotion options for Minimax TTS and update defaults to use automatic emotion selection.

[sourcery-ai]

Hey - 我在这里给出了一些高层面的反馈：

• 在现有配置可能仍在使用 neutral 的情况下，从 minimax-voice-emotion 选项中移除 neutral，可能会让用户感到困惑，或者破坏现有的 UI 选项选择；即使推荐将 auto 作为默认值，仍应考虑保留 neutral 作为一个可选项，以保证向后兼容性。

给 AI 代理的提示

Please address the comments from this code review:

## Overall Comments
- Removing `neutral` from the `minimax-voice-emotion` options while existing configs may still use it could confuse users or break existing UI selections; consider keeping `neutral` as a selectable option for backward compatibility even if `auto` is preferred as the default.

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Original comment in English

Hey - I've left some high level feedback:

• Removing neutral from the minimax-voice-emotion options while existing configs may still use it could confuse users or break existing UI selections; consider keeping neutral as a selectable option for backward compatibility even if auto is preferred as the default.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Removing `neutral` from the `minimax-voice-emotion` options while existing configs may still use it could confuse users or break existing UI selections; consider keeping `neutral` as a selectable option for backward compatibility even if `auto` is preferred as the default.

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