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).

docker-compose.yml

@@ -0,0 +1,23 @@
+services:
+  busbar-designer:
+    build: .
+    image: busbar-designer:latest
+    container_name: busbar-designer
+    restart: unless-stopped
+    ports:
+      - "5000:5000"             # change to "8000:5000" if 5000 is taken
+    environment:
+      - HOST=0.0.0.0
+      - PORT=5000
+      - FLASK_DEBUG=0
+      - BUSBAR_DB=/app/data/busbar.db
+      - SNAPSHOT_RETENTION=20    # max history versions kept per project
+    volumes:
+      - ./data:/app/data         # SQLite DB lives here; back it up by copying this folder
+    healthcheck:
+      test: ["CMD", "python", "-c",
+             "import urllib.request,sys; sys.exit(0 if urllib.request.urlopen('http://localhost:5000/api/health', timeout=3).status==200 else 1)"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 30s