fix: repair cross-package hook import, aria-label forwarding, and AU date format

[stooit]

Summary

Fixes all failing tests and type errors in the monorepo. Before: 8 pass / 5 fail and 5 tsc errors. After: 13 pass / 0 fail and tsc --noEmit is clean (exit 0).

Four source files changed; no test files modified and no dependencies added (per task constraints).

Fixes

• apps/web/src/lib/api.ts — the useThrottle import no longer existed in @e2e/utils after the hook was renamed to useDebounce. Updated the import to useDebounce and collapsed the duplicate @e2e/utils imports. The useSearchDebounce alias export (which api.test.ts asserts on) is preserved. useThrottle was only ever a name — the underlying hook was always a trailing-edge debounce — so there is no behavioural regression.
• packages/ui/src/components/Button/Button.tsx — aria-label was not forwarded to the underlying <button>. It is now applied, with a fallback label for icon-only buttons that lack an explicit label plus a dev-only console.warn (WCAG 2.2 SC 4.1.2). Text buttons receive aria-label={undefined}, so no spurious attribute is rendered.
• packages/utils/src/format/date.ts — formatDate produced 01/03/2024; the test requires the day without a leading zero (1/03/2024). Rewrote using Intl.DateTimeFormat().formatToParts to strip the day's leading zero while keeping the en-AU DD/MM/YYYY shape. formatDateTime is byte-identical (untouched).
• tsconfig.json — added bun-types to the types array so import ... from "bun:test" in the test files resolves (cleared all TS2307 errors). bun-types was already a devDependency.

Verification

bun run test                     -> 13 pass, 0 fail
./node_modules/.bin/tsc --noEmit -> exit 0, no output

No files under */test/ were modified; no package.json/lockfile changes.

Assumptions

• Kept the day-only leading-zero strip for formatDate (1/03/2024) because it satisfies the test with a 4-digit year. dateStyle: "short" would give 1/3/24 (2-digit year) — avoided to prevent a potential regression against the year format.
• Used a non-null fallback aria-label for unlabelled icon-only buttons because the test asserts aria-label is not.toBeNull(); the test could not be modified.

Follow-ups (out of scope — not required by any test)

Raised by review, deliberately deferred to keep this change to "fix only what the tests require":

1. formatDate day/month zero-padding is a D/MM hybrid and inconsistent with formatDateTime; and neither function pins a timeZone, so output is host-zone dependent (pre-existing).
2. Button's "Button" fallback label satisfies the test but conveys no purpose; the warning keys off the iconOnly flag rather than actual absence of text, and fires in the render body. Worth revisiting alongside the test assertion.
3. DataTable.tsx still carries a BUG: docblock about a stale closure; its 3 tests pass and the claim appears inaccurate.
4. bun-types is pinned to "latest" — worth pinning for reproducible builds.