feat: support configurable WeCom API base URL for reverse proxy deployment (#1890)

* Initial plan

* Add api_base_url support to WeCom API libraries and adapters

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

* Add api_base_url parameter to OAClient and adapters for Official Account and WeCom APIs

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>
Co-authored-by: Junyan Qin <rockchinq@gmail.com>

src/langbot/pkg/platform/sources/officialaccount.yaml

@@ -53,6 +53,16 @@ spec:
       type: string
       required: true
       default: "AI正在思考中，请发送任意内容获取回复。"
+    - name: api_base_url
+      label:
+        en_US: API Base URL
+        zh_Hans: API 基础 URL
+      description:
+        en_US: API Base URL, used for accessing the Official Account API. If you are deploying in an internal network environment and accessing the Official Account API through a reverse proxy, please fill in this item according to the documentation.
+        zh_Hans: 可选，若您部署在内网环境并通过反向代理访问微信公众号 API，可根据文档修改此项
+      type: string
+      required: false
+      default: "https://api.weixin.qq.com"
 execution:
   python:
     path: ./officialaccount.py