fix: 修复 bat 编码乱码、Config.html 打不开、missing scope 问题

- fix(bat): 所有 Windows .bat 文件加 UTF-8 BOM，修复中文乱码
  (portable 和 usb-release 共 7 个文件，close #3)
- fix(usb-release/Windows-Start.bat): 首次启动打开 Config.html
  时补加 file:/// 前缀，修复浏览器无法打开本地文件的问题
  (close #12)
- fix(Config.html): gateway.auth 加入 scopes: ['operator.admin']，
  修复配置模型时报 missing scope: operator.admin 错误
  (portable / usb-release / u-claw-app 三个版本同步，close #11)

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

usb-release/Windows-Start.bat

@@ -1,4 +1,4 @@
-@echo off
+@echo off
 setlocal EnableDelayedExpansion
 chcp 65001 >nul 2>&1
 title U-Claw - Portable AI Agent
@@ -103,7 +103,7 @@ if "!HAS_MODEL!"=="yes" (
     start /B "" cmd /c "timeout /t 3 /nobreak >nul && start http://127.0.0.1:!PORT!/#token=!TOKEN!"
 ) else (
     echo   First time setup - opening Config page in 3 seconds...
-    start /B "" cmd /c "timeout /t 3 /nobreak >nul && start %UCLAW_DIR%Config.html?port=!PORT!"
+    start /B "" cmd /c "timeout /t 3 /nobreak >nul && start file:///%UCLAW_DIR%Config.html?port=!PORT!"
 )
 
 REM Start gateway (foreground, blocks until stopped)