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/context/AppContext.js

@@ -0,0 +1,4 @@
+import { createContext, useContext } from 'react';
+
+export const AppContext = createContext(null);
+export const useApp = () => useContext(AppContext);