fix: Plugin Manager '+ Add Directory' khong hien folder picker (ban 1.1.3)

Nguyen nhan: UI that chay tren http://127.0.0.1:8000 (engine) nen
window.__TAURI__ KHONG ton tai (Tauri chi inject vao trang no serve -
src-tauri/ui/index.html chi la loader redirect). Fallback window.prompt
KHONG hoat dong trong WebView2 (no-op) -> khong co picker nao xuat hien.

Fix: in-app folder browser qua backend (co san /media/computer +
/media/browse trong media.py, auth qua apiRequest):
- services/api.js: them browseComputer() + browseDir(path)
- app.jsx PluginManagerModal: state pmPicker + overlay UI (roots/drives
  -> dirs -> 'Len' (parent) -> 'Chon thu muc nay' -> setPmDirs)
- Thu tu uu tien: __TAURI__.core.invoke('plugin:dialog|open') -> in-app
  browser -> prompt (fallback cuoi, browser thuan khong phai WebView2)
- Bump ?v= cache-bust index.html (api.js + app.precompiled.js)

Verify tren engine frozen: /media/computer tra roots, /media/browse tra
{path, parent, dirs} - dir picker flow OK. Skill da ghi lai:
~/.hermes/skills/software-development/sonicforge-daw-engine-packaging

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=202607271016"></script>
+    <script src="/static/js/services/api.js?v=202608091200"></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=202608081600" defer></script>
+    <script src="/static/js/app.precompiled.js?v=202608091200" defer></script>
     <link rel="stylesheet" href="/static/css/styles.css?v=202607271016">
     <style>
         :root {