Fix hardcoded API paths: inject URLs via url_for() in template, read from window.NEUSICIAN_URLS in api.js

templates/vue3_neusik/index.html

@@ -9,6 +9,15 @@
 <div id="score-editor-app"
      data-import-on-load="{{ import_on_load }}">
 </div>
+<script>
+window.NEUSICIAN_URLS = {
+    astlog:  "{{ url_for('get_static_astlog') }}",
+    score:   "{{ url_for('plain_text_score') }}",
+    status:  "{{ url_for('statusjson') }}",
+    result:  "{{ url_for('send_audio_generated') }}",
+    submit:  "{{ url_for('public-yaml-acceptor') }}"
+};
+</script>
 <script type="importmap">
 {
   "imports": {