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/dashboard.html

@@ -0,0 +1,88 @@
+{% extends "base.html" %}
+{% block title %}Dashboard — Battery Tracker{% endblock %}
+
+{% block content %}
+<h1>Battery Dashboard</h1>
+
+{% set total = batteries|length %}
+{% set available = batteries|selectattr('status','eq','available')|list|length %}
+{% set installed = batteries|selectattr('status','eq','installed')|list|length %}
+{% set retired  = batteries|selectattr('status','eq','retired')|list|length %}
+
+<div style="display:flex;gap:1rem;flex-wrap:wrap;margin-bottom:1.25rem;">
+  <div class="card" style="flex:1;min-width:120px;text-align:center;">
+    <div style="font-size:1.8rem;font-weight:700;">{{ total }}</div>
+    <div class="text-muted">Total</div>
+  </div>
+  <div class="card" style="flex:1;min-width:120px;text-align:center;">
+    <div style="font-size:1.8rem;font-weight:700;color:#166534;">{{ available }}</div>
+    <div class="text-muted">Available</div>
+  </div>
+  <div class="card" style="flex:1;min-width:120px;text-align:center;">
+    <div style="font-size:1.8rem;font-weight:700;color:#1e40af;">{{ installed }}</div>
+    <div class="text-muted">Installed</div>
+  </div>
+  <div class="card" style="flex:1;min-width:120px;text-align:center;">
+    <div style="font-size:1.8rem;font-weight:700;color:#64748b;">{{ retired }}</div>
+    <div class="text-muted">Retired</div>
+  </div>
+</div>
+
+<div class="card">
+  <div class="table-wrap">
+    <table>
+      <thead>
+        <tr>
+          <th>Label</th>
+          <th>Brand</th>
+          <th>Status</th>
+          <th>Assigned To</th>
+          <th>Actions</th>
+        </tr>
+      </thead>
+      <tbody>
+        {% for b in batteries %}
+        <tr>
+          <td><a href="{{ url_for('battery_detail', battery_id=b.id) }}"><strong>{{ b.label }}</strong></a></td>
+          <td>{{ b.brand }}</td>
+          <td>
+            <span class="badge badge-{{ b.status }}">{{ b.status|capitalize }}</span>
+          </td>
+          <td>
+            {% if b.device %}
+              <a href="{{ url_for('device_detail', device_id=b.device.id) }}">{{ b.device.name }}</a>
+              {% if b.device.has_mixed_brands() %}
+                <span class="badge badge-warning" title="Mixed brands in this device">⚠ mixed</span>
+              {% endif %}
+            {% else %}
+              <span class="text-muted">—</span>
+            {% endif %}
+          </td>
+          <td style="white-space:nowrap;">
+            <a class="btn btn-sm btn-secondary" href="{{ url_for('battery_detail', battery_id=b.id) }}">View</a>
+
+            {% if b.is_available() %}
+              <a class="btn btn-sm btn-primary" href="{{ url_for('battery_assign', battery_id=b.id) }}">Assign</a>
+            {% endif %}
+
+            {% if b.is_installed() %}
+              <form class="inline" method="post" action="{{ url_for('battery_unassign', battery_id=b.id) }}">
+                <button class="btn btn-sm btn-warning" type="submit">Unassign</button>
+              </form>
+            {% endif %}
+
+            {% if not b.is_retired() %}
+              <form class="inline" method="post" action="{{ url_for('battery_retire', battery_id=b.id) }}">
+                <button class="btn btn-sm btn-secondary" type="submit">Retire</button>
+              </form>
+            {% endif %}
+          </td>
+        </tr>
+        {% else %}
+        <tr><td colspan="5" class="text-muted" style="text-align:center;padding:1rem;">No batteries found. <a href="{{ url_for('battery_add') }}">Add one.</a></td></tr>
+        {% endfor %}
+      </tbody>
+    </table>
+  </div>
+</div>
+{% endblock %}