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.js

@@ -0,0 +1,23 @@
+// "Luke 1, Luke 2, Luke 3, Luke 5" -> "Luke 1–3, 5": a long run of chapters reads as ranges, so a
+// study card stays short. Anything that isn't "Book N" is left as it was.
+export function compactPassages(summary) {
+  if (!summary) return '';
+  const parts = summary.split(/,\s*/);
+  const groups = [];
+  for (const part of parts) {
+    const m = part.match(/^(.+?)\s+(\d+)$/);
+    if (!m) { groups.push({ raw: part }); continue; }
+    const last = groups[groups.length - 1];
+    if (last && last.book === m[1]) last.chapters.push(Number(m[2]));
+    else groups.push({ book: m[1], chapters: [Number(m[2])] });
+  }
+  return groups.map((g) => {
+    if (g.raw !== undefined) return g.raw;
+    const runs = [];
+    for (const n of g.chapters) {
+      const run = runs[runs.length - 1];
+      if (run && n === run[1] + 1) run[1] = n; else runs.push([n, n]);
+    }
+    return `${g.book} ${runs.map(([a, b]) => (a === b ? a : b === a + 1 ? `${a}, ${b}` : `${a}–${b}`)).join(', ')}`;
+  }).join(', ');
+}