chore: add unique assets from other branches into dan_branch

Bring hardware/spec content from drho1y-mvp_1 (3d_models, arduino_code, backend_control, kicad, specification) so dan_branch holds the shared union of branch files without rewriting other branch tips.

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

backend_control/create_venv.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+python -m venv testing
+
+source testing/bin/activate
+pip install -r requirements.txt