Add Outline stage, parallel reading, offline saves, backup, sync-conflict handling and more

Study
- New Outline stage (hierarchical I./A./1. points, linked to chunks, in all exports);
  the chunk stage is now "Chunks"
- Home cards: passages shown as ranges, tags capped with "+N more"

Reader
- Side-by-side translations and a Compare tab per verse
- Typeface, line spacing, verse-number settings; text and column scale with the screen
- Highlights/bookmarks sheet with named colours (synced); BSB footnote spacing fix
- Cmd-K palette (passages, studies, notes, marks), keyboard shortcuts and "?" help

Flow and safety
- Toasts with Undo replace most confirm()/alert()
- Back/Forward move between pages
- Server refuses saves over a newer copy (409); keep-mine / use-other banner;
  opening a study no longer re-stamps it
- Latest chapter request wins when flipping quickly

Offline and data
- Save books, plan days or a whole BSB/NET for offline
- Service worker fixes: helloao /api/ URLs were skipped and responses cloned too late
- Settings: download/restore a full backup

Accessibility
- Sheets trap focus and close on Escape, skip link, focus ring, reduced motion,
  theme contrast raised to 4.5:1 (with a test)

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

src/components/study/OutlineRail.jsx

@@ -8,7 +8,7 @@ export default function OutlineRail({ project, selectedId, onSelect, onEditOutli
   return (
     <nav aria-label="Chunks" className="flex h-full min-h-0 flex-col">
       <div className="flex items-center justify-between px-3 pb-2 pt-3">
-        <span className="text-[11px] uppercase tracking-wide text-[var(--r-sub)]">Outline</span>
+        <span className="text-[11px] uppercase tracking-wide text-[var(--r-sub)]">Chunks</span>
         <button type="button" onClick={onEditOutline} className="text-[11px] text-[var(--r-accent)] hover:underline">Edit</button>
       </div>
       <div className="min-h-0 flex-1 overflow-y-auto px-2 pb-4">