FEAT: Plugin Manager folder picker + scan dirs (Windows/macOS), docker .env paths, status bar adaptive tips, DSP Tool vao sub-tab audioclip

- Plugins Manager (Tools menu): Browse folder (Tauri dialog + fallback paste path), Save & Scan VST/SoundFont dirs -> plugin_dirs.json (user override, env la base)
- Docker: VST_DIR/SOUNDFONT_DIR/PIANOBK_DIR tu .env/docker-compose mount vao container + env cho engine/celery
- Status bar: bo label 'Scroll: Zoom' -> Adaptive tips (prHint + fallback text)
- DSP Tool: move vao SUB-TAB editor audioclip (Phase Inv / Swap L/R / Reverse + apply vung chon/ca clip)
- Tauri: them tauri-plugin-dialog + dialog:default permission cho folder picker

src-tauri/src/lib.rs

@@ -10,6 +10,7 @@ struct EngineProcess(Mutex<Option<CommandChild>>);
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_shell::init())
+        .plugin(tauri_plugin_dialog::init())
         .setup(|app| {
             // 1. Spawn sidecar daw_engine.exe (PyInstaller bundle)
             let sidecar_command = app