fix: repair cross-package test failures in monorepo

[stooit]

Summary

Fixes all 5 failing tests and eliminates all type errors across the monorepo. bun run test → 13 pass / 0 fail; bun x tsc --noEmit → exit 0. No test files modified, no dependencies added.

Changes

• apps/web/src/lib/api.ts — The importer referenced a non-existent useThrottle. Reconciled to import the actual useDebounce export from @e2e/utils and re-export it as useSearchDebounce, satisfying the api test and clearing TS2305.
• packages/ui/.../Button.tsx — aria-label was destructured but never applied to the DOM. Now forwarded; for iconOnly buttons without an explicit label it derives one from string children (falling back to "Button" with a dev-only warning), meeting WCAG 2.2 SC 4.1.2. Non-icon buttons keep their visible text as the accessible name.
• packages/ui/.../DataTable.tsx — Stale-closure sort bug: setSortDir read sortDir from the render-time closure, so descending never triggered on the second click. Replaced with a functional updater setSortDir(prev => prev === "asc" ? "desc" : "asc").
• packages/utils/.../date.ts — en-AU already produces correct day-first ordering; the only defect was ICU zero-padding the day (01/03/2024). Used formatToParts to strip padding from the day part only, so 1 March 2024 → 1/03/2024. formatDateTime and formatAUD untouched and still passing.
• tsconfig.json — Added "types": ["bun-types"] to resolve four pre-existing TS2307: Cannot find module 'bun:test' errors. bun-types was already a devDependency; moduleResolution: bundler with no types array meant it wasn't loaded. Verified no @types/* regressions (react/JSX/DOM/NodeJS.Timeout all still resolve).

Verification

bun run test  ->  13 pass, 0 fail, 17 expect() calls
bun x tsc --noEmit  ->  exit 0

Reviewed by the review agent: verdict COMMENT, no blocking issues; all four functional fixes verified correct and the tsconfig change confirmed necessary with no side effects.

Assumptions

• The task brief hinted a hook was "renamed to useThrottle"; the actual repo state was the reverse — useDebounce is the real export and api.ts was the stale importer. Fixed the importer (minimal change) rather than renaming the shared hook, since the api test imports from ../src/lib/api and expects useSearchDebounce there.
• The unlabelled icon-only Button test asserts aria-label must be non-null, so a derived/fallback label is required by the test; kept the dev warning to surface the underlying a11y concern to callers.