fix: repair cross-package test and type failures

[stooit]

Summary

Fixes all 9 failing tests and 5 tsc --noEmit errors across the monorepo. Bugs spanned packages/ui, packages/utils, apps/web, plus two test-environment config gaps.

Result: bun test → 13 pass / 0 fail (was 4 pass / 9 fail); tsc --noEmit → clean (was 5 errors).

Changes (5 files, +34/−32)

• apps/web/src/lib/api.ts — hook was renamed useThrottle → useDebounce in packages/utils; updated the import. The public useSearchDebounce alias is unchanged, so no consumer contract shifts.
• packages/ui/src/components/Button/Button.tsx — apply aria-label, with an iconOnly fallback and a dev-only warning (WCAG 2.2 SC 4.1.2, ES8 aligned).
• packages/utils/src/format/date.ts — use Intl.DateTimeFormat.formatToParts to emit an unpadded day under en-AU (1/03/2024, not 01/03/2024).
• bunfig.toml — preload the happy-dom setup so @testing-library/react has a DOM (the old [test].environment key is inert in Bun; DOM tests were erroring with document is not defined).
• tsconfig.json — add bun-types so import ... from "bun:test" resolves.

Constraints honoured

• No test files modified.
• No dependencies added (no package.json / lockfile changes).
• Only what the tests require was changed.

Assumptions

• Verified locally that no non-test consumer imports the old useThrottle name.
• Kept formatDateTime untouched as it was not under test.

Reviewer follow-ups (out of scope; not test-required)

• W1 — the iconOnly aria-label fallback resolves to a generic "Button" to satisfy the (unmodifiable) test. Type-level enforcement (discriminated union on iconOnly) is cleaner but fails Button.test.tsx, so it is blocked by the "don't modify tests" constraint. Recommend descriptive labels at call sites.
• W3 — formatDate (4-digit year) and formatDateTime (2-digit year) use different conventions; worth aligning.
• W4 — formatDate is locale-pinned (en-AU) but not timezone-stable; adding timeZone: "Australia/Sydney" would make output deterministic.