feat: extract collapsible container into partial

templates/_partials/_collapsible.html.twig

@@ -0,0 +1,35 @@
+{#
+    Collapsible section with a heading trigger and a chevron.
+
+    heading      string  visible heading text (required)
+    id           string  unique per page; wires aria-controls (required)
+    open         bool    initial state (default false)
+    headingLevel int     aria-level of the heading (default 2)
+    contentClass string  classes on the body wrapper (default 'rte-content')
+    storageKey   string  persist open state in sessionStorage (default '')
+#}
+<div {{ stimulus_controller('toggle',
+        { 'open': open|default(false), 'storageKey': storageKey|default('') },
+        { 'closed': 'hidden', 'iconOpen': 'rotate-180' }) }}>
+    <button type="button"
+            class="flex items-center justify-between w-full text-left"
+            data-action="toggle#toggle"
+            data-toggle-target="trigger"
+            aria-expanded="{{ open|default(false) ? 'true' : 'false' }}"
+            aria-controls="{{ id }}-content">
+        <span class="block text-2xl md:text-3xl font-bold mb-2"
+              role="heading"
+              aria-level="{{ headingLevel|default(2) }}">
+            {{ heading }}
+        </span>
+        <span class="shrink-0 transition-transform" data-toggle-target="icon">
+            {{ icon('chevron-down', 'w-5 h-5') }}
+        </span>
+    </button>
+
+    <div id="{{ id }}-content"
+         class="{{ contentClass|default('rte-content') }}"
+         data-toggle-target="content">
+        {% block body %}{% endblock %}
+    </div>
+</div>