fix(export): offline render dong export panel + hien progress timeline

renderMasteringExport khong tu dong export panel/progress (chi bounce cu
lam). triggerWavExport: nhanh offline render -> setShowExportPanel(false),
setShowExportProgress(true), setExportProgress(-1) truoc khi goi, reset
progress trong finally.

app/static/js/app.jsx

@@ -28001,7 +28001,16 @@ const App = () => {
       // xuất file 1 note rồi câm / câm hẳn) → chỉ dùng làm fallback khi server lỗi.
       if (midiTracks.length > 0 && exportSettings.source === 'project' && exportSettings.format === 'wav') {
         if (serverStatus === 'connected') {
-          await renderMasteringExport();
+          // Đóng export panel + hiện progress timeline (renderMasteringExport
+          // không tự đóng — bounce cũ có làm).
+          setShowExportPanel(false);
+          setShowExportProgress(true);
+          setExportProgress(-1);
+          try {
+            await renderMasteringExport();
+          } finally {
+            setShowExportProgress(false);
+          }
           return;
         }
         if (!cacheOK) {