fix: refuse deleting a document assigned to a season task

templates/administrative/system/document/index.html.twig

@@ -31,6 +31,7 @@
                 </thead>
                 <tbody>
                 {% for document in pagination %}
+                    {% set assignments = seasonTaskDocuments[document.id] ?? [] %}
                     <tr>
                         <td>
                             {{ document.displayName ? document.displayName : document.originalFilename }}
@@ -38,7 +39,10 @@
                         <td>
                             {# A slot belongs to exactly one document, so this is what tells staff
                                which file a feature actually picks up. #}
-                            {{ document.token ? document.token.label() : '-' }}
+                            {% set usages = (document.token ? [document.token.label()] : [])|merge(
+                                assignments|filter(a => a.task)|map(a => 'Saisonteam: ' ~ a.task.label())
+                            ) %}
+                            {{ usages is empty ? '-' : usages|join(', ') }}
                         </td>
                         <td>
                             {{ document.size|file_size }}
@@ -51,13 +55,21 @@
                         </td>
                         <td>
                             <div class="flex items-center space-x-2 justify-end">
-                                <button type="button"
-                                        class="text-red-500"
-                                        hx-get="{{ path('app_administrative_system_document_delete', { 'uuid': document.uuid }) }}"
-                                        hx-target="body"
-                                        hx-swap="beforeend">
-                                    {{ icon('delete') }}
-                                </button>
+                                {% if assignments is empty %}
+                                    <button type="button"
+                                            class="text-red-500"
+                                            hx-get="{{ path('app_administrative_system_document_delete', { 'uuid': document.uuid }) }}"
+                                            hx-target="body"
+                                            hx-swap="beforeend">
+                                        {{ icon('delete') }}
+                                    </button>
+                                {% else %}
+                                    {# Held by a NOT NULL foreign key; replace it under Saisonteam-Dokumente first. #}
+                                    <span class="text-gray-300 cursor-not-allowed"
+                                          title="Als Saisonteam-Dokument hinterlegt, kann nicht gelöscht werden">
+                                        {{ icon('delete') }}
+                                    </span>
+                                {% endif %}
                                 <button type="button"
                                         hx-get="{{ path('app_administrative_system_document_replace', { 'uuid': document.uuid }) }}"
                                         hx-target="body"