feat: tách luồng âm instrument theo môi trường — docker dùng FluidSynthWASM, standalone dùng native pyfluidsynth (+Carla VSTi)

- runtime: detect()/capabilities() trả environment (docker|standalone)
- vst_engine: render_soundfont_midi_to_audio (pyfluidsynth native, event-stream, release tail)
- plugins: POST /soundfont-render — render MIDI notes -> WAV (auth, fallback default SF)
- frontend: SonicRuntime.environment + dataset.environment; app.jsx route preview/transport:
  standalone+SF -> soundfont-render WAV (playNativeSfNote/scheduleNativeSfItem),
  docker giữ WASM, VSTi standalone giữ Carla bridge

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=202608101904" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202608101914" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {