ezdxf, matplotlib, and other Python libs try to write into $HOME/.config
and $HOME/.cache. With ProtectHome=true the real /home/busbar is invisible
to the service and pathlib.Path.exists() throws PermissionError.
Fix: set HOME, XDG_CONFIG_HOME, XDG_CACHE_HOME to /opt/busbar-designer/data/*
which is already in ReadWritePaths. Hardening (ProtectHome) stays intact.
install.sh also pre-creates the .config / .cache subdirs.
Web tool for designing nickel/copper busbars over cylindrical-cell battery
packs (21700, 18650) in hex holders. Flask + build123d backend exports
STEP/DXF/SVG; vanilla JS frontend with live preview, multi-project SQLite
persistence, snapshot history.
Deploy scripts in deploy/ (proxmox-lxc.sh, install.sh, update.sh).
wenil