chore(ui): remove 2 dead components (Breadcrumbs, ScrollFlow) with zero real import sites

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Context

Two fully-implemented, documented components have zero real import sites anywhere in apps/loopover-ui/src:

• components/site/breadcrumbs.tsx:11-14 — doc comment claims it's the "Consistent breadcrumb rail used on /app, /docs, /api headers," but a repo-wide grep -rn "Breadcrumbs" returns only its own definition.
• components/site/scroll-flow.tsx:19 — a fully implemented, IntersectionObserver-driven scroll-linked step component, also with zero import sites anywhere in src/.

Requirements

• Confirm via a fresh repo-wide search that both components (and any exported helpers specific to them) have zero real callers.
• Remove both files and their dedicated test files, if any.
• If either component turns out to describe a page header/interaction that genuinely SHOULD exist today (e.g. Breadcrumbs' own doc comment claims it's used on /app, /docs, /api — verify none of those pages actually need it before deleting; if one clearly should have it, wire it in instead of deleting), note that in the PR and wire it in rather than deleting — but only if a genuine current gap is found, not speculatively.

Deliverables

• Breadcrumbs and ScrollFlow either removed (if confirmed dead) or wired into a genuine real call site (if one is found missing it).

Expected Outcome

No orphaned, unused components remain in apps/loopover-ui/src/components/site.

Links & Resources

• apps/loopover-ui/src/components/site/breadcrumbs.tsx:11-14
• apps/loopover-ui/src/components/site/scroll-flow.tsx:19

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JSO-4291