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>

server/prefs.js

@@ -5,6 +5,8 @@ const ENUMS = {
   theme: ['paper', 'sepia', 'dark'],
   translation: ['BSB', 'ESV', 'NLT', 'CSB', 'NASB', 'NET'],
   layout: ['flow', 'verses'],
+  startPage: ['studies', 'reader', 'plans'], // where the app opens and where Home buttons go
+  planTranslation: ['same', 'BSB', 'ESV', 'NLT', 'CSB', 'NASB', 'NET'], // which Bible new reading plans start in
   commentarySource: ['matthew-henry', 'john-gill', 'jamieson-fausset-brown', 'tyndale', 'adam-clarke', 'john-calvin', 'keil-delitzsch'],
 };
 const DAY_MS = 86_400_000;