Initial commit: Busbar Designer

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).

Dockerfile

@@ -0,0 +1,50 @@
+# Multi-stage to keep the runtime image small.
+# build123d pulls scipy + matplotlib + OCP wheel — a few hundred MB.
+
+FROM python:3.12-slim AS builder
+
+ENV PIP_NO_CACHE_DIR=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        build-essential libgl1 libglu1-mesa libxrender1 libxext6 libsm6 \
+        libgomp1 \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --user -r requirements.txt && \
+    pip install --user gunicorn
+
+# ---------------------------------------------------------------------------
+
+FROM python:3.12-slim AS runtime
+
+# OCP needs these at runtime.
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libgl1 libglu1-mesa libxrender1 libxext6 libsm6 libgomp1 \
+    && rm -rf /var/lib/apt/lists/* \
+    && useradd --create-home --shell /usr/sbin/nologin app
+
+COPY --from=builder /root/.local /home/app/.local
+ENV PATH=/home/app/.local/bin:$PATH \
+    PYTHONUNBUFFERED=1 \
+    HOST=0.0.0.0 \
+    PORT=5000 \
+    FLASK_DEBUG=0
+
+WORKDIR /app
+COPY --chown=app:app app.py busbar_export.py ./
+COPY --chown=app:app static/ ./static/
+
+USER app
+EXPOSE 5000
+
+# SQLite DB lives here; mount as a volume to persist across container restarts.
+ENV BUSBAR_DB=/app/data/busbar.db
+VOLUME /app/data
+
+# 2 workers is plenty — each export is CPU-bound on OpenCASCADE; more workers
+# don't help on a single-socket VM and just balloon RAM.
+CMD ["gunicorn", "--bind=0.0.0.0:5000", "--workers=2", "--threads=2", \
+     "--timeout=120", "app:app"]