Second (last) jQuery/BS4 JS blocker to the BS5 CSS swap. Replaces the
`bootstrap-carousel-swipe` jQuery plugin + `$(...).carousel()` init with
react-bootstrap's <Carousel> (native swipe, no jQuery) for both home carousels.
- Preserves the progressive `.lazy` background mechanism (blur -> full image on
slide-in): the old `slide.bs.carousel` handler becomes <Carousel onSlide>,
which marks the incoming index in component state.
- Keeps all per-slide class hooks (carousel-item-N, carousel-snd-item-N).
- CSS ports in Index-custom.scss for react-bootstrap's BS5 markup: indicators
render as <button> (not <li>), and prev/next labels use .visually-hidden
(BS4 had .sr-only) -> add a shim so labels stay hidden on current BS4 CSS.
- Drops the now-unused bootstrap-carousel-swipe dependency.
Full-app build boots clean. Needs a visual staging check of the home page.