Use setenv in launcher scripts, add requirements.txt and missing .sh scripts

platz.bat/platz.sh now derive PLATZ via setenv instead of hardcoded
paths, matching the Standard Programm Template already applied to
setenv/install_py/activate_venv/get_cmd. Added the missing .sh
counterparts to those .bat scripts, an empty requirements.txt for
install_py to install (project only uses the stdlib), and ignore
entries for .venv/, out/, .vscode/, *.swp.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

bin/activate_venv.bat

@@ -0,0 +1,20 @@
+@echo off
+REM ================================================================
+REM TEST - Python Virtual Environment aktivieren
+REM ================================================================
+
+call "%~dp0setenv.bat"
+
+if not exist "%PLATZ%\.venv" (
+    echo FEHLER: Virtual environment nicht gefunden.
+    echo Bitte zuerst bin\install_py.bat ausfuehren.
+    exit /b 1
+)
+
+call "%PLATZ%\.venv\Scripts\activate.bat"
+echo Virtuelle Umgebung aktiviert.
+echo Python-Version:
+python --version
+echo.
+echo Installierte Pakete:
+pip list