fix: nut Synth tren TCP khong hien danh sach VSTi da scan (ban 1.1.5)

- Nut Synth TCP goi openInstrumentSelector (modal 'Select Instrument')
  nhung modal chi co category SoundFont + GM - khong co muc VST (muc VST
  chi ton tai o dropdown MixerStrip). Them 'VST Instruments' vao sidebar
  trai modal: list instrumentSelectorData.vst_instruments (listPlugins),
  click -> setTrackInstrumentWithUndo(trackId, v.id, v.name) + dong modal.
- _scan_vst_in_dirs + /scan: phat hien ca FOLDER ten X.vst3 (Windows VST3
  = folder chua X.vst3.dll) - truoc day chi scan file.
- Ghi chu: pedalboard (engine VST) la headless - KHONG mo duoc GUI goc cua
  plugin; danh sach + chon la co che chon nhac cu kha thi.

Verify engine frozen: /plugins/available tra ['PadMachine','UltraSynth']
(ca file va folder .vst3); /scan dong bo; test_plugin_api 3 passed.

app/templates/index.html

@@ -31,7 +31,7 @@
     <script src="https://unpkg.com/react@18.3.1/umd/react.production.min.js"></script>
     <script src="https://unpkg.com/react-dom@18.3.1/umd/react-dom.production.min.js"></script>
     <script src="/static/js/services/fluidsynthLoader.js?v=202607271245"></script>
-    <script src="/static/js/services/api.js?v=202608091300"></script>
+    <script src="/static/js/services/api.js?v=202608091400"></script>
     <script src="/static/js/services/audioEngine.js?v=202607271016"></script>
     <script src="/static/js/services/storage.js?v=202608038200"></script>
     <script src="/static/js/services/soundfontStorage.js?v=202607271016"></script>
@@ -43,7 +43,7 @@
     <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=202608091300" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202608091400" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {