Fix: eagerload series.sets i admin og API (MissingGreenlet i async mode)

backend/app/templates/series.html

@@ -0,0 +1,31 @@
+{% extends "base.html" %}
+{% block title %}Serier{% endblock %}
+{% block content %}
+<h1>📦 Pokémon TCG serier</h1>
+<p style="color:var(--text-muted);margin-bottom:24px;">{{ series|length }} serie(r)</p>
+
+<div class="card-grid">
+    {% for serie in series %}
+    <a href="/series/{{ serie.name|urlencode }}" class="card-set">
+        <div class="card">
+            <h3 style="margin-bottom:6px;">{{ serie.name }}</h3>
+            <p style="font-size:0.85rem;color:var(--text-muted);">
+                {{ serie.sets|length }} sæt ·
+                {% set ns = namespace(total=0) %}
+                {% for s in serie.sets %}{% set ns.total = ns.total + s.cards|length %}{% endfor %}
+                {{ ns.total }} kort
+            </p>
+            {% if serie.description %}
+            <p style="font-size:0.85rem;color:var(--text-muted);margin-top:6px;">{{ serie.description }}</p>
+            {% endif %}
+        </div>
+    </a>
+    {% endfor %}
+</div>
+
+{% if series|length == 0 %}
+<div class="card" style="text-align:center;color:var(--text-muted);">
+    <p>Ingen serier endnu.</p>
+</div>
+{% endif %}
+{% endblock %}