feat: add email notifications, order references, stock badges, and sale flags

- Add customer email field and PayPal payment reminder emails with order reference (HEL-YEAR-ID format)
- Display stock availability with color-coded badges (available/low/unavailable)
- Add sale/clearance flag with animated red badge overlay
- Implement automatic fallback placeholder for missing/broken product images
- Add email column to order management view

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

wawi/templates/orders.html

@@ -16,6 +16,7 @@
           <th>Datum</th>
           <th>Name</th>
           <th>Handy</th>
+          <th>E-Mail</th>
           <th>Mannschaft</th>
           <th>Artikel</th>
           <th>Größe</th>
@@ -33,6 +34,7 @@
             <td>{{ o.created_at }}</td>
             <td>{{ o.name }}</td>
             <td>{{ o.handy }}</td>
+            <td>{{ o.email or "–" }}</td>
             <td>{{ o.mannschaft }}</td>
             <td>{{ o.artikel }}</td>
             <td>{{ o.groesse }}</td>
@@ -43,7 +45,8 @@
               {% endif %}
             </td>
             <td>
-              {% if o.payment_status == "paid" %}<span class="badge success">Bezahlt</span>
+              {% if o.canceled %}–
+              {% elif o.payment_status == "paid" %}<span class="badge success">Bezahlt</span>
               {% else %}<span class="badge warning">Unbezahlt</span>
               {% endif %}
             </td>
@@ -68,7 +71,7 @@
                 {% endif %}
                 <form method="post" action="{{ url_for('bp.cancel_order', order_id=o.id) }}" onsubmit="return confirm('Bestellung wirklich stornieren?');">
                   <input type="hidden" name="csrf_token" value="{{ csrf_token() }}"/>
-                  <button class="btn small danger" type="submit">Stornieren</button>
+                  <button class="btn small danger" type="submit">Storno</button>
                 </form>
               {% else %}
                 –
@@ -76,7 +79,7 @@
             </td>
           </tr>
           <tr class="order-history">
-            <td colspan="12">
+            <td colspan="13">
               <details class="inline-details">
                 <summary>Historie</summary>
                 <div class="history-grid">
@@ -92,7 +95,7 @@
           </tr>
         {% else %}
           <tr>
-            <td colspan="12" class="empty">Keine Bestellungen.</td>
+            <td colspan="13" class="empty">Keine Bestellungen.</td>
           </tr>
         {% endfor %}
       </tbody>