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/utils/passageSummary.test.js

@@ -0,0 +1,17 @@
+import { expect, test } from 'vitest';
+import { compactPassages } from './passageSummary.js';
+
+test('runs of chapters become ranges', () => {
+  expect(compactPassages('Luke 1, Luke 2, Luke 3, Luke 4, Luke 5, Luke 6')).toBe('Luke 1–6');
+  expect(compactPassages('1 John 1, 1 John 2, 1 John 3, 1 John 4, 1 John 5')).toBe('1 John 1–5');
+});
+test('gaps stay separate, pairs and singles stay plain', () => {
+  expect(compactPassages('Luke 1, Luke 2, Luke 3, Luke 5')).toBe('Luke 1–3, 5');
+  expect(compactPassages('Malachi 1, Malachi 2')).toBe('Malachi 1, 2');
+  expect(compactPassages('John 3')).toBe('John 3');
+});
+test('several books, and text that is not a chapter, are kept', () => {
+  expect(compactPassages('Ephesians 1, Ephesians 2, Ephesians 3, Titus 1')).toBe('Ephesians 1–3, Titus 1');
+  expect(compactPassages('Whole book')).toBe('Whole book');
+  expect(compactPassages('')).toBe('');
+});