Move import state into ImportPage; share translation list via hook

The session-list import form, preview, and runEpisodeImport now live in
ImportPage. useAvailableTranslations fetches the translation list once per
visit for both Import and Setup. Drops the never-read importFile state.

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

src/App.test.jsx

@@ -497,3 +497,18 @@ describe('Admin page', () => {
     expect(screen.queryByRole('button', { name: /admin/i })).not.toBeInTheDocument();
   });
 });
+
+// ---------------------------------------------------------------------------
+// Import page (state is local to ImportPage)
+// ---------------------------------------------------------------------------
+describe('Import page', () => {
+  test('opens from Home, lists fetched translations, and goes back', async () => {
+    const user = userEvent.setup();
+    await renderApp();
+    await user.click(screen.getByRole('button', { name: /import session list/i }));
+    expect(await screen.findByRole('heading', { name: /import session list/i })).toBeInTheDocument();
+    expect(await screen.findByRole('option', { name: 'KJV' })).toBeInTheDocument();
+    await user.click(screen.getByRole('button', { name: /back/i }));
+    expect(await screen.findByRole('button', { name: /import session list/i })).toBeInTheDocument();
+  });
+});