Add PyQt6 UI skeleton with theming and setup scripts

install_all_python.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env sh
+# Install Python dependencies system-wide or in the active environment.
+set -eu
+
+PYTHON_BIN=${PYTHON_BIN:-python3}
+
+"$PYTHON_BIN" -m pip install --upgrade pip
+"$PYTHON_BIN" -m pip install -r requirements.txt