feat: implement automatic auth credential updates

[bbbugg]

中文说明

功能更新:

1. 自动凭证更新: 实现了将最新的 Cookie 和 LocalStorage 自动写回 auth-x.json 的功能，防止会话过期。

配置项:

• 新增环境变量 ENABLE_AUTH_UPDATE（默认 false）。
• 仅当设置为 true 时，才会在登录成功或每 24 小时自动更新 Auth 文件。

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English Summary

Features:

1. Auto Credential Persistence: Implemented automatic write-back of fresh Cookies/LocalStorage to auth-x.json to prevent session expiration.

Configuration:

• Added ENABLE_AUTH_UPDATE environment variable (default: false).
• Auth files are only updated on login or every 24 hours when this is set to true.

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• fix [建议]: 增加 Auth 凭证自动回写/保活功能，实现长期免维护 #18

follow-up pr #23

[Copilot]

Pull request overview

This PR implements an automatic authentication credential update feature that periodically saves refreshed cookies and localStorage back to auth-x.json files to prevent session expiration. The feature is controlled by a new ENABLE_AUTH_UPDATE environment variable (default: false) and triggers updates on successful login/account switch and every 24 hours via the health monitor.

Changes:

• Added ENABLE_AUTH_UPDATE configuration flag with environment variable parsing
• Implemented _updateAuthFile() method to write current browser storage state back to auth files
• Integrated periodic auth updates (24-hour interval) into the health monitor
• Updated documentation in both English and Chinese READMEs

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/utils/ConfigLoader.js	Adds enableAuthUpdate config property with environment variable parsing and logging
src/core/BrowserManager.js	Implements _updateAuthFile() method and integrates auth updates on login and every 24 hours
src/auth/AuthSource.js	Improves error message clarity by adding "(parse error)" label
README.md	Documents new ENABLE_AUTH_UPDATE environment variable in Chinese
README_EN.md	Documents new ENABLE_AUTH_UPDATE environment variable in English

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[github-actions]

🎉 此 PR 的修改已在版本 v0.4.0 中发布。
🎉 The changes in this PR have been released in version v0.4.0.