feat: add WeChat QR code login to config-server

Add in-app WeChat scanning via Tencent iLink API:
- server.js: QR code PNG renderer, WeChat API proxy, plugin auto-install
- index.html: WeChat channel card with QR display and polling UI
- Windows-Start.bat: auto-install WeChat plugin on startup
- Windows-Install.bat: copy WeChat plugin during installation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

portable/Windows-Start.bat

@@ -71,6 +71,19 @@ if not exist "%CORE_DIR%\node_modules" (
     echo.
 )
 
+REM Auto-install WeChat plugin if available
+set "WECHAT_PLUGIN_SRC=%APP_DIR%\extensions\openclaw-weixin"
+set "WECHAT_PLUGIN_DST=%USERPROFILE%\.openclaw\extensions\openclaw-weixin"
+if exist "%WECHAT_PLUGIN_SRC%\openclaw.plugin.json" (
+    if not exist "%WECHAT_PLUGIN_DST%\openclaw.plugin.json" (
+        echo   Installing WeChat plugin...
+        mkdir "%USERPROFILE%\.openclaw\extensions" 2>nul
+        xcopy /s /e /q /y "%WECHAT_PLUGIN_SRC%" "%WECHAT_PLUGIN_DST%\" >nul
+        echo   WeChat plugin installed!
+        echo.
+    )
+)
+
 REM Find available port
 set PORT=18789
 :check_port