Rename the Export stage to Finish

It now holds files, sharing, handouts, slides, importing notes, schedule,
co-teachers and earlier versions, not just exports.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/test/App.pages.test.jsx

@@ -26,7 +26,7 @@ describe('Back to the dashboard', () => {
     await dashboard();
   });
 
-  test.each(['Chunks', 'Study', 'Outline', 'Script', 'Export'])('the %s stage of a study', async (stage) => {
+  test.each(['Chunks', 'Study', 'Outline', 'Script', 'Finish'])('the %s stage of a study', async (stage) => {
     const u = await loadChapter();
     addChunk('Paul, a servant', 'In hope of eternal');
     await screen.findByText('1 created');