fix: 本地viewer不会解析配置文件的环境变量

[xutao0565]

Pre-submission checklist | 提交前检查

• I have searched existing issues and this hasn't been mentioned before | 我已搜索现有问题，确认此问题尚未被提及
• I have read the project documentation and confirmed this issue doesn't already exist | 我已阅读项目文档并确认此问题尚未存在
• This issue is specific to MemOS and not a general software issue | 该问题是针对 MemOS 的，而不是一般软件问题

Bug Description | 问题描述

本地插件viewer直接从配置文件读取配置，不会解析环境变量，导致Embedding等模型的key必须硬编码在配置文件中

How to Reproduce | 如何重现

以openclaw为例，openclaw.json文件Embedding 模型的key替换成变量,Viewer界面连接报错

Environment | 环境信息

• Operating System : macos V26.4.1
• Memos Version: memos-local-openclaw-plugin v1.0.9-beta.2

Additional Context | 其他信息

No response

Willingness to Implement | 实现意愿

• I'm willing to implement this myself | 我愿意自己解决
• I would like someone else to implement this | 我希望其他人来解决

[MaiHHConnect]

💬 我也在做记忆系统相关的工作：CausaMem，可以来看看，说不定有能借鉴的地方 🙂