Add cross-reference map, admin health page, passkeys and device list, settings tabs

- Reader: chapter cross-reference map (M) from IQ Bible's reference graph
- Admin: Health tab with disk use, snapshots (back up, download, restore), failure logs
- Passkey sign-in (WebAuthn), signed-in device list, sign out others, optional sign-in alerts
- Settings split into Account, Preferences, Notifications, Security, Your data tabs
- ntfy server field: catch a topic typed into the server box

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

src/test/App.pages.test.jsx

@@ -130,6 +130,7 @@ describe('Chosen home page', () => {
     await renderApp();
     await u.click(await screen.findByRole('button', { name: /account menu/i }));
     await u.click(await screen.findByRole('menuitem', { name: /settings/i }));
+    await u.click(await screen.findByRole('tab', { name: 'Preferences' }));
     const prefs = within(await screen.findByRole('region', { name: 'Preferences' }));
     await u.click(within(prefs.getByRole('group', { name: 'Home page' })).getByRole('button', { name: 'Reading Plans' }));
     expect(localStorage.getItem('start-page')).toBe('plans');