bug: cindy账号登录后，会把已有提供商清除

### 问题描述 / What happened

cindy账号登录后，会把第三方key清除，正在运行中的任务也会消失不见

### 环境 / Environment

- Cindy 版本或 commit / version or commit:0.1.22
- 平台与版本 / platform & OS version:window 10
- 安装方式 / install method:win exe

### 复现步骤 / Steps to reproduce

1.先填入自定义提供商
2.运行一个任务
3.cindy手机号登录

### 日志与截图 / Logs & screenshots

_No response_

Reproduce the issue in the Windows executable using the reported sequence: configure a custom provider, start a task, then sign in with a Cindy phone account. Trace the login flow and the state handling for providers and active tasks. Done means signing in preserves the existing provider configuration and the running task remains visible and active.

Written by the indexing model from the issue text.