Initial commit: Flask battery tracker app

- Flask + SQLAlchemy (MariaDB-compatible schema) battery tracking web app
- 40 pre-seeded batteries (Eneloop, BONAI, Energizer NiMH) across 5 devices
- Business rules: block retired assignment, brand-mix warnings, capacity checks
- Mobile-friendly Jinja2 templates with inline CSS
- waitress WSGI server via systemd user service (sbin/install-service.sh)
- SQLite → MariaDB migration script (migrate_to_mariadb.py)
- 26 passing acceptance tests (pytest + Flask test client)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

sbin/install-service.sh

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+# install-service.sh
+# Generates and installs a systemd user-level service for the Battery Tracker app.
+# No root required — uses ~/.config/systemd/user/.
+#
+# Usage:  bash sbin/install-service.sh
+
+set -euo pipefail
+
+# Resolve the app root directory from the script's own location
+APP_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+VENV_WAITRESS="$APP_DIR/.venv/bin/waitress-serve"
+SERVICE_DIR="$HOME/.config/systemd/user"
+SERVICE_FILE="$SERVICE_DIR/battery-tracker.service"
+
+echo "=== Battery Tracker — systemd user service installer ==="
+echo "App directory: $APP_DIR"
+echo
+
+# Sanity checks
+if [[ ! -f "$VENV_WAITRESS" ]]; then
+  echo "ERROR: waitress-serve not found at $VENV_WAITRESS"
+  echo "Run:  python3 -m venv .venv && .venv/bin/pip install -r requirements.txt"
+  exit 1
+fi
+
+if [[ ! -f "$APP_DIR/app.py" ]]; then
+  echo "ERROR: app.py not found in $APP_DIR"
+  exit 1
+fi
+
+# Prompt for port and host
+read -rp "Listen host [default: 127.0.0.1]: " HOST
+HOST="${HOST:-127.0.0.1}"
+
+read -rp "Listen port [default: 5000]: " PORT
+PORT="${PORT:-5000}"
+
+echo
+echo "Generating service file → $SERVICE_FILE"
+
+mkdir -p "$SERVICE_DIR"
+
+cat > "$SERVICE_FILE" <<EOF
+[Unit]
+Description=Battery Tracker Flask App
+After=network.target
+
+[Service]
+Type=simple
+WorkingDirectory=$APP_DIR
+ExecStart=$VENV_WAITRESS --host=$HOST --port=$PORT app:app
+Environment=PYTHONPATH=$APP_DIR
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=default.target
+EOF
+
+echo "Service file written."
+echo
+
+# Reload and enable
+systemctl --user daemon-reload
+systemctl --user enable battery-tracker
+
+echo
+echo "=== Done ==="
+echo
+echo "Start the service:   systemctl --user start battery-tracker"
+echo "Check status:        systemctl --user status battery-tracker"
+echo "View logs:           journalctl --user -u battery-tracker -f"
+echo "Stop the service:    systemctl --user stop battery-tracker"
+echo
+echo "To uninstall:"
+echo "  systemctl --user disable --now battery-tracker"
+echo "  rm $SERVICE_FILE"
+echo "  systemctl --user daemon-reload"