Track last time a session was open in the session_store

### Describe the feature or problem you'd like to solve

Computer restarts and I need to restore my sessions. Love to review the sessions that were open to recover them.

### Proposed solution

Add a last_open column of type time to session store. Every 5 minutes, update the time in the column. Then I can see when each session was open regardless of whether I took any action in it.

### Example prompts or workflows

show me all the sessions that were open today
show me all the sessions that were open last week
look at all the open sessions from today - is any of them related to feature X?

### Additional context

_No response_

该 issue 提到了 session_store，但没有提供文件或测试路径。先定位该 store 和 session 生命周期的入口点，然后检查重启后 session 的持久化和查询方式。完成标准是定期记录上次打开时间，并通过测试支持所述的今天和上周 session 工作流。

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