[Bug]: APAC Region support for LangSmith

[YouGhee]

Description

While setup, OpenWiki prompts the LangSmith region options as US and EU, but not APAC.

LangSmith officially supports three regions on GCP, and one region on AWS.

Steps to Reproduce

1. openwiki --init
2. Configure LLM provider
3. Enable and configure LangSmith traces

Expected Behavior

Here's the base URL of APAC region - https://apac.api.smith.langchain.com/
This may be shown along with US and EU

Actual Behavior

LangSmith region options displayed are US and EU only.

Environment

• OS: MacOS Tahoe
• Node.js version: v22.13.1
• OpenWiki version: v0.3.1

Additional Context

No response

[sudipawtg]

Taking this — adding APAC (https://apac.api.smith.langchain.com) to the LangSmith region options, setup serialize/deserialize, and allowlisted hosts.