fix: repair cross-package bugs so all tests and types pass

[stooit]

Summary

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

Bugs fixed

• utils — renamed hook / broken import. apps/web/src/lib/api.ts imported a debounce hook name that no longer existed (tsc: no exported member; api test: expected useSearchDebounce). Reconciled the export in @e2e/utils so useSearchDebounce is exported and the app import resolves.
• ui/Button — missing a11y attribute. Icon-only buttons now forward aria-label to the underlying <button>, satisfying the accessible-label test.
• ui/DataTable — stale closure. Sort handler captured stale state; switched to a functional state updater so the controlled re-render test passes.
• utils/date — wrong locale/format. formatDate now uses en-AU dateStyle: "short", matching the expected 1/03/2024-style output instead of the previous 01/03/2024.
• tsconfig — bun:test types. Added bun-types (existing dep) to compilerOptions.types so the bun:test import in test files resolves under tsc --noEmit. No test files were touched.

Verification

• bun run test — 13 pass, 0 fail
• npx tsc --noEmit — exit 0, no output

Assumptions

• The tests are the source of truth for expected behaviour (format string, exported hook name, aria attribute). Source was changed to match tests; no test files were edited.
• en-AU locale chosen because it produces the exact expected day/month ordering with a non-zero-padded day.