Add one-click installers for admin and user batch scripts

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

seediso/windows11/50-Install-NSIS-Admin.bat

@@ -5,14 +5,14 @@ title Install NSIS
 fltmc >nul 2>&1
 if errorlevel 1 (
     echo Please right-click this file and choose "Run as administrator".
-    pause
+    if not defined INSTALL_ALL pause
     exit /b 1
 )
 
 where winget.exe >nul 2>&1
 if errorlevel 1 (
     echo winget was not found.
-    pause
+    if not defined INSTALL_ALL pause
     exit /b 1
 )
 
@@ -28,5 +28,5 @@ if "%RC%"=="0" (
 ) else (
     echo winget exited with code %RC%.
 )
-pause
+if not defined INSTALL_ALL pause
 exit /b %RC%