feat(dashboard): add full-size media preview

tests/dashboard/media.test.tsx

@@ -106,6 +106,21 @@ describe('media page', () => {
     expect(await screen.findByRole('img', { name: 'Media from alice' })).toHaveClass('is-blurred');
   });
 
+  it('opens revealed media in a dismissible full-size preview', async () => {
+    installMediaApi();
+    const user = userEvent.setup();
+    renderMedia();
+
+    await user.click(await screen.findByRole('button', { name: 'Reveal media from alice' }));
+    await user.click(screen.getByRole('button', { name: 'View media from alice larger' }));
+
+    const dialog = screen.getByRole('dialog', { name: 'Media from alice' });
+    expect(within(dialog).getByRole('img', { name: 'Media from alice' })).toHaveAttribute('src', '/media/one.jpg');
+
+    await user.keyboard('{Escape}');
+    expect(screen.queryByRole('dialog', { name: 'Media from alice' })).not.toBeInTheDocument();
+  });
+
   it('filters by conversation, sender, media type, and age with an explicit no-match state', async () => {
     installMediaApi();
     const user = userEvent.setup();