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>

templates/battery_detail.html

@@ -0,0 +1,70 @@
+{% extends "base.html" %}
+{% block title %}{{ battery.label }} — Battery Tracker{% endblock %}
+
+{% block content %}
+<h1>{{ battery.label }}</h1>
+
+<div class="card">
+  <table style="width:auto;border:none;">
+    <tr>
+      <td style="padding:0.3rem 1rem 0.3rem 0;font-weight:600;color:#64748b;border:none;">Label</td>
+      <td style="border:none;">{{ battery.label }}</td>
+    </tr>
+    <tr>
+      <td style="padding:0.3rem 1rem 0.3rem 0;font-weight:600;color:#64748b;border:none;">Brand</td>
+      <td style="border:none;">{{ battery.brand }}</td>
+    </tr>
+    <tr>
+      <td style="padding:0.3rem 1rem 0.3rem 0;font-weight:600;color:#64748b;border:none;">Status</td>
+      <td style="border:none;"><span class="badge badge-{{ battery.status }}">{{ battery.status|capitalize }}</span></td>
+    </tr>
+    <tr>
+      <td style="padding:0.3rem 1rem 0.3rem 0;font-weight:600;color:#64748b;border:none;">Device</td>
+      <td style="border:none;">
+        {% if battery.device %}
+          <a href="{{ url_for('device_detail', device_id=battery.device.id) }}">{{ battery.device.name }}</a>
+        {% else %}
+          <span class="text-muted">None</span>
+        {% endif %}
+      </td>
+    </tr>
+  </table>
+</div>
+
+<!-- Notes -->
+<div class="card">
+  <h2>Notes</h2>
+  <form method="post" action="{{ url_for('battery_edit_notes', battery_id=battery.id) }}">
+    <div class="form-group">
+      <textarea name="notes" placeholder="No notes yet…">{{ battery.notes or '' }}</textarea>
+    </div>
+    <button class="btn btn-primary" type="submit">Save Notes</button>
+  </form>
+</div>
+
+<!-- Actions -->
+<div class="card">
+  <h2>Actions</h2>
+  <div class="form-actions">
+    {% if battery.is_available() %}
+      <a class="btn btn-primary" href="{{ url_for('battery_assign', battery_id=battery.id) }}">Assign to Device</a>
+    {% endif %}
+
+    {% if battery.is_installed() %}
+      <form method="post" action="{{ url_for('battery_unassign', battery_id=battery.id) }}">
+        <button class="btn btn-warning" type="submit">Unassign</button>
+      </form>
+    {% endif %}
+
+    {% if not battery.is_retired() %}
+      <form method="post" action="{{ url_for('battery_retire', battery_id=battery.id) }}">
+        <button class="btn btn-secondary" type="submit">Retire Battery</button>
+      </form>
+    {% endif %}
+
+    <a class="btn btn-danger" href="{{ url_for('battery_delete', battery_id=battery.id) }}">Delete Battery</a>
+  </div>
+</div>
+
+<a class="text-muted" href="{{ url_for('dashboard') }}">&larr; Back to Dashboard</a>
+{% endblock %}