docs: add Langfuse observability to documentation

[jannikmaierhoefer]

💻 变更类型 | Change Type

• ✨ feat
• 🐛 fix
• ♻️ refactor
• 💄 style
• 👷 build
• ⚡️ perf
• 📝 docs
• 🔨 chore

🔀 变更说明 | Description of Change

Hi there, since LobeChat has a Langfuse integration for observability, I added a documentation page that describes how to set this up. 🙂

I would suggest to place it under "Advance Usage" in the Docs. However, I did not find the config file that edits the sidebar. It would be great if you could add this to my PR!

📝 补充信息 | Additional Information

If you have any additional questions, you can also reach out to me via our shared Discord channel with you! I am also happy to provide a Chinese version of the page if you think this would make sense :)

[vercel]

@jannikmaierhoefer is attempting to deploy a commit to the LobeChat Community Team on Vercel.

A member of the Team first needs to authorize it.

[lobehubbot]

👍 @jannikmaierhoefer

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