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

[stooit]

Summary

Fixes all 9 failing tests and all tsc --noEmit type errors across the monorepo (packages/ui, packages/utils, apps/web). Bugs spanned multiple packages. No test files modified; no new dependencies added.

Before: 4 pass / 9 fail, 5 tsc errors.
After: 13 pass / 0 fail, 0 tsc errors.

Bugs fixed

1. Renamed hook out of sync (packages/utils, apps/web) — a hook was renamed but apps/web/src/lib/api.ts still imported the old useThrottle, while the test expected useSearchDebounce. Exported useSearchDebounce (alias of the canonical useDebounce) and corrected the importer.
2. DOM test environment not registered (packages/ui) — bun test from the repo root failed every render() with document is not defined. The root bunfig.toml used the invalid environment = "happy-dom" key (Jest/Vitest syntax, silently ignored by Bun). Replaced with a preload that runs the existing (unmodified) happy-dom GlobalRegistrator setup script.
3. Missing accessibility attribute (packages/ui/Button) — icon-only buttons now forward aria-label and receive a fallback accessible name when unlabelled. Decorative icons are hidden with aria-hidden only when the button already has a name from another source, so an icon-only-content button never ends up with an empty accessible name [WCAG 2.2 SC 4.1.2].
4. Stale-closure sort bug (packages/ui/DataTable) — collapsed sort key + direction into a single SortState object updated via one pure functional updater, so direction is always derived from the same snapshot as its key. Eliminates the latent batched-update hazard; no StrictMode double-toggle.
5. Wrong date format (packages/utils/date) — formatDate returned 01/03/2024 (padded day). Kept the en-AU locale for correct D/M ordering and stripped the ICU-forced day padding via formatToParts, so 1 March 2024 -> 1/03/2024 as the test requires.

Type errors

• bun:test module-not-found (4 files) resolved by wiring the already-installed bun-types into tsconfig.json types (no new dependency).
• useThrottle missing-export error resolved by fix fix: resolve all failing tests and type errors across monorepo #1.

Verification

bun test -> 13 pass / 0 fail. ./node_modules/.bin/tsc --noEmit -> exit 0.
(The console.warn seen in test output is expected — a Button test deliberately renders an unlabelled icon-only button.)

Assumptions

• The canonical hook name the codebase settled on is useSearchDebounce (what the test asserts); useDebounce is retained as the underlying implementation.
• Standard AU date is DD/MM/YYYY, but the test asserts an unpadded day (/^1/), so the format is intentionally D/MM/YYYY to satisfy the test without modifying it.

Follow-ups (non-blocking, out of scope)

• DataTable sortable <th> has an onClick but no keyboard affordance (pre-existing; SC 2.1.1) — should wrap in a <button>.
• Consider making aria-label a compile-time required prop on unlabelled icon buttons (breaking API change) rather than a runtime warning.