Add audiowidget endpoint: Blueprint renders audiowidget.tmpl, PaneCP fetches it on synthesis completion

templates/vue3_neusik/audiowidget.tmpl.stub

@@ -0,0 +1,18 @@
+{# audiowidget.tmpl.stub — copy to audiowidget.tmpl in the same directory to activate.
+   Customise to match your site's look and feel.
+
+   Context variables (passed as query params by the score editor):
+     result_url  – URL of the rendered MP3, or empty string
+     errors      – synthesis error message, or empty string
+#}
+{% if errors %}
+  <div class="se-error">{{ errors }}</div>
+{% elif result_url %}
+  <figure class="audio-result">
+    <figcaption>Rendered result</figcaption>
+    <audio controls preload="metadata" style="display:block;width:100%">
+      <source src="{{ result_url }}" type="audio/mpeg">
+      <a href="{{ result_url }}">Download MP3</a>
+    </audio>
+  </figure>
+{% endif %}