fix: remove duplicate back links on detail pages now covered by Breadcrumb (#238)

[Ayinkx]

Description

Fixes #238.

Both detail pages (src/app/anchors/[id]/page.tsx and src/app/settlements/[id]/page.tsx) already render a Breadcrumb (with a link back to the parent list) immediately above the detail component. AnchorDetail and SettlementDetail still rendered their own standalone ← Back to anchors / ← Back to settlements link at the top of their markup — a leftover from before Breadcrumb was added — resulting in two stacked "go back" affordances on every detail page.

What changed

• Removed the leading <Link href="/anchors">← Back to anchors</Link> block from src/components/AnchorDetail.tsx.
• Removed the leading <Link href="/settlements">← Back to settlements</Link> block from src/components/SettlementDetail.tsx.
• Dropped the now-obsolete assertions on those links from AnchorDetail.test.tsx and SettlementDetail.test.tsx.
• No change to data-loading, deactivate/execute/cancel, or ConfirmDialog behavior.

Call-site check

Per the issue's requirement, I confirmed neither component is used anywhere else without a Breadcrumb:

• AnchorDetail — used only by src/app/anchors/[id]/page.tsx (renders Breadcrumb).
• SettlementDetail — used only by src/app/settlements/[id]/page.tsx (renders Breadcrumb).

A grep across src/ found no other call sites. The src/app/anchors/[id]/loading.tsx and src/app/settlements/[id]/loading.tsx files render their own back-link during the loading state and don't render a Breadcrumb, so they are intentionally untouched (as the issue notes).

Note on the 404 branch

The not-found message inside each component still renders its inline Back to anchors / Back to settlements link (inside the error card). That link is context-specific ("this record was not found") and is not the redundant top-of-page link described in the issue, so it was kept.

Acceptance criteria

• AnchorDetail and SettlementDetail no longer render their own "← Back to X" link.
• The Breadcrumb on both detail pages remains the sole back-navigation affordance.
• Existing tests are updated and continue to pass.

Test evidence

npx vitest run src/components/AnchorDetail.test.tsx src/components/SettlementDetail.test.tsx:

Test Files  1 failed | 1 passed (2)
     Tests  1 failed | 15 passed (16)

The single failure (disables Execute and Cancel while settlement action is pending in SettlementDetail.test.tsx) is a pre-existing, timing-sensitive test that also fails on clean main (verified via git stash); it is unrelated to this change.

Full-suite comparison against clean main (both run locally):

• main: 10 test files failed, 48 tests failed / 577 passed
• this branch: 9 test files failed, 47 tests failed / 578 passed

The remaining failures (e.g. src/lib/wallet.test.ts SecurityError localStorage spying) exist on main and are untouched by this PR.

npx tsc --noEmit: 15 pre-existing errors, none in the changed files (identical count on main).

npx eslint on the four changed files: 3 pre-existing @typescript-eslint/no-explicit-any errors on untouched lines (identical on main); no new warnings/errors introduced.

Checklist

• CHANGELOG.md entry added under [Unreleased] (this PR changes user-facing behavior: removes the redundant link).
• Tests updated for the change.