Easier navigation on iPhone

- Phones get a bottom tab bar (Studies, Bible, Plans, Prayer, Account); wider screens keep the header nav
- The Account menu opens upward from the bar; toasts sit above it
- Reader and study pages get a labelled Home button instead of a small arrow

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

src/components/reader/ReaderBars.jsx

@@ -1,6 +1,7 @@
 // Top and bottom chrome for the reader. Everything stays one tap away; focus
 // mode hides both.
 import { ChevronLeft, ChevronRight, ChevronDown, SearchIcon, LinkIcon, PenIcon, HeadphonesIcon, FocusIcon, CheckIcon, CompareIcon, HighlighterIcon } from './icons.jsx';
+import HomeButton from './HomeButton.jsx';
 import { BookmarkIcon } from '../../utils/bibleUtils.jsx';
 
 const iconBtn = 'flex h-9 w-9 items-center justify-center rounded-lg text-[var(--r-sub)] transition hover:bg-black/5 disabled:opacity-30 disabled:hover:bg-transparent';
@@ -9,7 +10,7 @@ export function TopBar({ title, onBack, onOpenNavigator, onSearch, onBookmarks,
   return (
     <div className="safe-top sticky top-0 z-30 border-b border-[var(--r-line)] bg-[var(--r-bar)] font-sans">
       <div className="mx-auto flex h-12 max-w-4xl items-center gap-1 px-2">
-        <button type="button" onClick={onBack} className="flex h-9 items-center gap-0.5 rounded-lg pl-1 pr-2 text-[var(--r-sub)] transition hover:bg-black/5" aria-label="Back to home" data-tip="Back to home"><ChevronLeft /><span className="hidden text-xs sm:inline">Home</span></button>
+        <HomeButton onClick={onBack} />
         <button type="button" onClick={onOpenNavigator}
           className="mx-auto flex min-w-0 items-center gap-1.5 rounded-lg px-3 py-1.5 text-sm font-medium text-[var(--r-text)] hover:bg-black/5" data-tip="Go to a book and chapter (G)">
           <span className="truncate">{title}</span><ChevronDown />