Add Windows installer packaging (Setup.exe + portable exe)

PyInstaller onedir/onefile specs, Inno Setup script, and GitHub Actions
workflow to produce JUC500-Setup-win64.exe and portable builds.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/setup_windows.bat

@@ -0,0 +1,16 @@
+@echo off
+setlocal
+cd /d %~dp0..
+
+py -3 -m venv .venv
+call .venv\Scripts\activate.bat
+python -m pip install -U pip
+pip install -r requirements.txt
+pip install -e .
+
+echo.
+echo Setup done. Next:
+echo   .venv\Scripts\activate
+echo   python -m juc500_xfer info
+echo See docs\WINDOWS.md for Zadig / WinUSB steps.
+endlocal