Preferences in Settings and a home page the user chooses

Settings gets a Preferences section: theme, default Bible, the Bible new reading
plans start in, verse layout, commentary, text size, reading width, audio
narrator (the last three stay per device; text size and narrator are now
remembered). A Home page setting (My Studies, Bible Reader or Reading Plans)
decides where the app opens and where every Home button goes; already being
there means My Studies. Back arrows are labelled Home. Tests cover every page
leading back.

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

src/App.jsx

@@ -71,7 +71,7 @@ const App = () => {
       reader.stopMarksSync();
       reader.stopPrefsSync();
       setProjectIndex(switchStorageUser(null));
-      goHome();
+      goStudies();
     },
   });
   const library = useProjectLibrary({
@@ -174,7 +174,7 @@ const App = () => {
   // player) so this works even without opening the reader first.
   const listenReadingPlanDay = (bookAbbrev, chapter) => {
     audio.handlePlayBookAudioFrom(bookAbbrev, chapter);
-    goHome();
+    goStudies();
   };
 
   // Builds a new chunk-builder project seeded with a reading-plan day's
@@ -228,12 +228,34 @@ const App = () => {
     setCurrentPage('import');
   };
 
-  const goHome = () => {
+  // The My Studies page.
+  const goStudies = () => {
     setProjectIndex(loadProjectIndex());
     setCurrentPage('home');
     setProject(null);
   };
 
+  // "Home": the page the user chose in Settings (My Studies, the Bible Reader, or Reading
+  // Plans). If they're already on it, Home means My Studies, so there is always somewhere to go.
+  const START_PAGES = { studies: 'home', reader: 'reader', plans: 'reading-plans' };
+  const goHome = () => {
+    const target = START_PAGES[reader.startPagePref] ?? 'home';
+    if (target === 'home' || target === currentPage) { goStudies(); return; }
+    setProjectIndex(loadProjectIndex());
+    setProject(null);
+    setCurrentPage(target);
+  };
+
+  // Open the app on the chosen home page (once, as soon as we know who is signed in).
+  const openedStartPageRef = useRef(false);
+  useEffect(() => {
+    if (authUser === undefined || openedStartPageRef.current) return;
+    openedStartPageRef.current = true;
+    const target = START_PAGES[reader.startPagePref] ?? 'home';
+    if (target !== 'home') setCurrentPage(target);
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [authUser]);
+
   // Manual retry after a failed background sync (shown in the project header).
   const retrySync = async () => {
     if (!project) return;
@@ -251,6 +273,7 @@ const App = () => {
     // Navigation
     currentPage, setCurrentPage,
     goHome,
+    goStudies,
     authServerDown,
     // Auth (login/2FA/settings form state lives in AuthPage and SettingsPage)
     authUser, setAuthUser,