Revert "feat: add batch operation functionality for session management"

[advent259141]

Reverts #4194

Summary by Sourcery

从后端 API 和控制台 UI 中移除最近新增的批量会话管理和分组功能，恢复之前更简单的会话管理行为。

Enhancements:

• 通过移除“列出所有带状态”的接口、批量更新操作以及分组管理端点，简化会话管理路由。
• 通过移除批量操作控件和自定义分组管理（以及相关文案/翻译），精简“会话管理”页面的 UI。

Original summary in English

Summary by Sourcery

Remove recently added batch session management and grouping functionality from both backend APIs and the dashboard UI, restoring the previous simpler session management behavior.

Enhancements:

• Simplify session management routes by dropping list-all-with-status, batch update operations, and group management endpoints.
• Streamline the Session Management page UI by removing batch operation controls and custom group management, along with related translations.

[sourcery-ai]

Hey - 我已经review了你的改动，一切看起来都很棒！

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Original comment in English

Hey - I've reviewed your changes and they look great!

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