Merge pull request #6816 from TIANQIAN1238/feat-document-webdav-env

docs: describe WHITE_WEBDAV_ENDPOINTS in .env.template

Author: Leizhenpeng

.env.template

@@ -74,6 +74,8 @@ ANTHROPIC_API_VERSION=
 ANTHROPIC_URL=
 
 ### (optional)
+### Whitelist of allowed WebDAV endpoints for chat-log sync, separated by comma.
+### Each entry must be a complete endpoint, e.g. https://dav.example.com/path
 WHITE_WEBDAV_ENDPOINTS=
 
 ### siliconflow Api key (optional)