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/hooks/usePrefsSync.test.js

@@ -19,7 +19,7 @@ function setup({ canApplyPosition = () => true, initial = {} } = {}) {
     const [layout, setLayout] = useState(initial.layout ?? 'flow');
     const [position, setPosition] = useState(initial.position ?? { book: 'GEN', chapter: 1 });
     const sync = usePrefsSync({
-      values: { theme, translation: 'BSB', layout, commentarySource: 'matthew-henry', position },
+      values: { theme, translation: 'BSB', layout, commentarySource: 'matthew-henry', planTranslation: 'same', startPage: 'studies', position },
       apply: (key, v) => { if (key === 'theme') setTheme(v); else if (key === 'layout') setLayout(v); else if (key === 'position') setPosition(v); },
       canApplyPosition,
     });
@@ -45,7 +45,7 @@ test('a device with no history takes the account\'s settings; a first device upl
   await act(async () => { await h.result.current.pullServerPrefs(); });
   expect(h.result.current.theme).toBe('sepia');
   // keys the account doesn't have yet are filled in from this device
-  expect(Object.keys(remote.puts[0]).sort()).toEqual(['commentarySource', 'layout', 'position', 'translation']);
+  expect(Object.keys(remote.puts[0]).sort()).toEqual(['commentarySource', 'layout', 'planTranslation', 'position', 'startPage', 'translation']);
 });
 
 test('reading position is not moved under you while the Reader is open', async () => {