Start every page at the top

The scroll position of the previous page used to carry over, which on iPad makes the
system blur the app bar when content is scrolled under it.

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

src/App.test.jsx

@@ -1420,3 +1420,19 @@ describe('System chrome follows the theme', () => {
     expect(document.documentElement.style.colorScheme).toBe('light');
   });
 });
+
+describe('New pages start at the top', () => {
+  test('moving to another page resets the scroll position', async () => {
+    const user = userEvent.setup();
+    await renderApp();
+    const scroller = document.scrollingElement ?? document.documentElement;
+    scroller.scrollTop = 480; // scrolled down on the dashboard
+    await user.click(screen.getByRole('button', { name: /reading plans/i }));
+    await screen.findByRole('heading', { name: /^reading plans$/i });
+    expect(scroller.scrollTop).toBe(0);
+    scroller.scrollTop = 300;
+    await user.click(screen.getByRole('button', { name: /back to home/i }));
+    await screen.findByText('My Studies');
+    expect(scroller.scrollTop).toBe(0);
+  });
+});