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/README.md

@@ -0,0 +1,43 @@
+# sbin — Support Scripts
+
+## install-service.sh
+
+Generates a systemd **user-level** service file and enables it. No root required.
+
+**Prerequisites:** The app's `.venv` must exist and have Flask installed.
+
+```bash
+bash sbin/install-service.sh
+```
+
+You will be prompted for a host (default `127.0.0.1`) and port (default `5000`).
+The script writes `~/.config/systemd/user/battery-tracker.service` and enables it.
+
+**Start the service:**
+```bash
+systemctl --user start battery-tracker
+systemctl --user status battery-tracker
+```
+
+**View live logs:**
+```bash
+journalctl --user -u battery-tracker -f
+```
+
+**Make it start on login** (requires lingering to be enabled for your user):
+```bash
+loginctl enable-linger "$USER"
+```
+
+**Uninstall:**
+```bash
+systemctl --user disable --now battery-tracker
+rm ~/.config/systemd/user/battery-tracker.service
+systemctl --user daemon-reload
+```
+
+**Re-run to update** (e.g. if you moved the app directory):
+```bash
+bash sbin/install-service.sh
+systemctl --user restart battery-tracker
+```