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

[stooit]

Summary

Fixes all failing tests and eliminates all type errors across the monorepo (packages/ui, packages/utils, apps/web). Result: 13 pass / 0 fail and tsc --noEmit exits clean.

The correct test invocation (per package.json) is:
bun test packages/utils/test packages/ui/test apps/web/test --preload ./packages/ui/test/setup.ts
A bare bun test fails with document is not defined because it skips the happy-dom preload — a runner-invocation artifact, not a source bug.

Bugs fixed

1. Renamed hook not exported (packages/utils/src/index.ts, apps/web/src/lib/api.ts) — tests and api.ts expected useSearchDebounce from @e2e/utils, but it wasn't exported; api.ts also imported a non-existent useThrottle (TS2305). Reconciled to the correct hook and export name.
2. Missing accessibility attribute (packages/ui/src/components/Button/Button.tsx) — icon-only buttons now pass aria-label/button props through to the rendered element.
3. Wrong date format (packages/utils/src/format/date.ts) — now produces en-AU D/MM/YYYY (no leading zero on the day). Uses UTC getters so output is timezone-stable (a naive local-time fix would break on AU-offset machines even though it passes in UTC CI).
4. bun:test type resolution (tsconfig.json) — added "types": ["bun-types"] so the bun:test import in test files type-checks. Config-only; no test files modified.

DataTable's stale-closure re-render test was verified to pass without changes under the correct preload command.

Assumptions

• The intended test command is the one defined in package.json (with the happy-dom preload), not a bare bun test.
• The hook's canonical exported name should be useSearchDebounce (what the tests assert); api.ts was the stale consumer.
• en-AU D/MM/YYYY (day-before-month, no leading zero on the day) is the expected formatDate output.

Verification

• bun test ... --preload ./packages/ui/test/setup.ts → 13 pass / 0 fail
• bunx tsc --noEmit → 0 errors

Constraints honoured

No test files modified, no dependencies added. Changes: 5 files, +9/-14.