FIX: 3 bugs - soundfont engine fallback, media explorer icons/drag, carla midi playback routing

- render_engine: soundfont track không có plugin_id giờ vẫn dùng instrument sf2 thay vì rơi về wave synth
- fontawesome: sửa đường dẫn webfonts (bỏ ../) hết 404 icon
- media explorer: drag MIDI library items vào timeline tạo được midi item (sinh 6 MIDI loop mẫu + resolve drop file)
- app.jsx: 3 path gate window.SonicSF cho phép route playback qua SonicCarlaMidi

app/templates/index.html

@@ -46,7 +46,7 @@
     <script src="/static/js/services/midiExtractor.js?v=202607281052"></script>
     <script src="/static/js/services/promptTemplateManager.js?v=202607281039"></script>
     <script src="/static/js/services/undoRedoEngine.js?v=202607290941"></script>
-    <script src="/static/js/app.precompiled.js?v=202608101840" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202608101904" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {