[Feature]: 增加定时任务的运行细节

## Summary

定时任务的运行情况需要根据详细的细节展示.

比如这个, 只有在失败的时候会给出信息, 如果一个任务时间比较长, 比较5-10分钟, 在此期间, 你是不知道这个任务有没有准时触发, 是否还在运行等等的信息. 希望增加根据细致的记录, 包括 开始时间, 运行时长, 结束时间, 运行结果等

## Component(s) Affected

- [x] Core / Backend (app, agents, config, providers, utils, local_models)
- [ ] Console (frontend web UI)
- [ ] Channels (DingTalk, Feishu, QQ, Discord, iMessage, etc.)
- [ ] Skills
- [ ] CLI
- [ ] Documentation (website)
- [ ] Tests
- [ ] CI/CD
- [ ] Scripts / Deploy

## Problem / Motivation

[What problem does this solve? Who benefits?]

## Proposed Solution

[Describe the feature or change you have in mind. Be as specific as possible.]

## Alternatives Considered

[Any other approaches or workarounds you thought about.]

## Additional Context

[Screenshots, examples, links to docs or similar features elsewhere.]

## Willing to Contribute

- [ ] I am willing to open a PR for this feature (after discussion).

The issue names no files, tests, or entry points. Start by locating the Core/Backend implementation for scheduled tasks and tracing how execution status is surfaced; done means exposing each task's start time, duration, end time, and result, including while a long-running task is still active.

Vom Indexierungsmodell aus dem Issue-Text verfasst.