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.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# ================================================================
+# Python Virtual Environment aktivieren
+# ================================================================
+
+source "$(dirname "${BASH_SOURCE[0]}")/setenv.sh"
+
+if [ ! -d "$PLATZ/.venv" ]; then
+    echo "FEHLER: Virtual environment nicht gefunden."
+    echo "Bitte zuerst bin/install_py.sh ausfuehren."
+    return 1 2>/dev/null || exit 1
+fi
+
+source "$PLATZ/.venv/bin/activate"
+echo "Virtuelle Umgebung aktiviert."
+echo "Python-Version:"
+python --version
+echo ""
+echo "Installierte Pakete:"
+pip list