add bash start script with pyhton/pip updates

start.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Always run from this script's directory.
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+cd "$SCRIPT_DIR"
+
+VENV_DIR=".venv"
+
+if command -v python3 >/dev/null 2>&1; then
+  PYTHON_BIN="python3"
+elif command -v python >/dev/null 2>&1; then
+  PYTHON_BIN="python"
+else
+  echo "Error: Python was not found on PATH."
+  exit 1
+fi
+
+echo "Using Python: $PYTHON_BIN"
+
+if [[ ! -x "$VENV_DIR/bin/python" ]]; then
+  if [[ -d "$VENV_DIR" ]]; then
+    echo "Existing virtual environment is not compatible with this OS. Recreating $VENV_DIR ..."
+    rm -rf "$VENV_DIR"
+  fi
+  echo "Creating virtual environment in $VENV_DIR ..."
+  "$PYTHON_BIN" -m venv "$VENV_DIR"
+fi
+
+VENV_PYTHON="$VENV_DIR/bin/python"
+
+echo "Upgrading pip and packaging tools ..."
+"$VENV_PYTHON" -m pip install --upgrade pip
+
+echo "Installing requirements ..."
+"$VENV_PYTHON" -m pip install -r requirements.txt
+
+echo "Starting program ..."
+"$VENV_PYTHON" -m src.taetigkeitsnachweis.cli