Split App.jsx into pages + add service worker for offline support

App.jsx reduced from ~6,500 to ~3,900 lines by extracting each route into its
own page component (AdminPage, AuthPage, HomePage, ImportPage, ReaderPage,
SettingsPage, SetupPage, StudyPage). State and handlers are shared via
AppContext (React Context API); AppRouter handles routing at module level.

Also adds a network-first service worker (public/sw.js) that caches the last-
fetched Bible chapter data from bible.helloao.org and bolls.life so the app
stays usable when those APIs are temporarily unreachable.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.jsx

@@ -3,6 +3,10 @@ import ReactDOM from 'react-dom/client';
 import App from './App.jsx';
 import './index.css';
 
+if ('serviceWorker' in navigator) {
+  navigator.serviceWorker.register('/sw.js').catch(() => {});
+}
+
 ReactDOM.createRoot(document.getElementById('root')).render(
   <StrictMode>
     <App />