Add fixed bottom chunk nav and IndexedDB Bible search cache

- Replace non-functional sticky nav with a fixed bottom bar (position: fixed)
  that stays visible while scrolling long study notes; hides in draw mode
- Add pb-20 to main so the bar never covers the last study section
- Cache whole-Bible search index (BSB complete.json, ~7MB) in IndexedDB
  with a 7-day TTL so repeated searches skip the network fetch entirely

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SUGGESTIONS.md

@@ -22,10 +22,8 @@ _Refreshed 2026-07-06 (multiple passes) — items already shipped have been remo
 ## UX / UI
 
 ### Study Page
-- **Sticky bottom nav** — top Prev/Next chunk nav shipped (commit `103e20c`); a matching sticky bottom bar for long chunks would avoid scroll-back
 
 ### Reader
-- **Whole-Bible search index isn't persisted** — the ~7MB `complete.json` fetch is cached in-memory only for the session; a page reload re-downloads it. Worth persisting to IndexedDB (not localStorage — too small) if this gets used often
 - **Bookmark color picker is still an emoji button** (🎨) — the bookmark/copy icons became proper SVGs, but color-cycling didn't get the same treatment
 
 ### Home Page