Version history, notes on highlights and bookmarks, "you've studied this", prayer journal

- Earlier versions of a study: the server keeps compressed copies (about one per ten minutes of
  editing, the latest 30); Export shows what differs and puts one back (the replaced copy is kept)
- Notes on highlights and bookmarks: synced, merged without loss, in exports and backups
- Reader verse panel lists your studies and chunks that cover the verse, and opens them
- Prayer journal: requests, who for, linked verses, days prayed, answers; synced, in backups
  and the account export; daily prayer reminder through ntfy
- TODO.md lists the ideas not built yet

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

src/components/study/PageShell.jsx

@@ -10,6 +10,7 @@ const NAV = [
   { id: 'studies', label: 'Studies', short: 'Studies' },
   { id: 'reader', label: 'Read Bible', short: 'Bible' },
   { id: 'plans', label: 'Reading Plans', short: 'Plans' },
+  { id: 'prayer', label: 'Prayer', short: 'Prayer' },
 ];
 
 // Avatar button with a dropdown: who you are, the theme, Settings, Admin, Log out.
@@ -62,8 +63,8 @@ function AccountMenu() {
 }
 
 export default function PageShell({ title, onBack, actions, active = null, maxWidth = 'max-w-6xl', children }) {
-  const { readerTheme, goHome, goStudies, openBibleReader, openReadingPlans, openPalette } = useApp();
-  const go = { studies: goStudies, reader: openBibleReader, plans: openReadingPlans };
+  const { readerTheme, goHome, goStudies, openBibleReader, openReadingPlans, openPrayer, openPalette } = useApp();
+  const go = { studies: goStudies, reader: openBibleReader, plans: openReadingPlans, prayer: openPrayer };
   return (
     <div className="min-h-dvh bg-[var(--r-bg)] font-sans text-[var(--r-text)]" style={themeVars(readerTheme)}>
       <a href="#content" className="skip-link">Skip to content</a>