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

.env.example

@@ -15,3 +15,11 @@ DEFAULT_ADMIN_PASSWORD=thay-mat-khau-admin
 
 # Storage (đường dẫn trong container)
 STORAGE_DIR=/app/app/storage
+
+# ── Plugin directories ──
+# Đường dẫn HOST tới thư mục chứa VST / SoundFont / Pianobook — dùng trong
+# docker-compose.yml để mount vào container (đổi theo máy chạy Docker).
+# Mặc định: /home/locpham/daw_assets/...
+VST_DIR=/home/locpham/daw_assets/vst3
+SOUNDFONT_DIR=/home/locpham/daw_assets/soundfonts
+PIANOBK_DIR=/home/locpham/daw_assets/pianobook