fix: repair cross-package test failures in monorepo

[stooit]

Summary

Fixes all 9 failing tests and the one real type error across the three-package monorepo (packages/ui, packages/utils, apps/web). bun test now reports 13 pass / 0 fail.

Fixes

Area	File	Fix
Test env	bunfig.toml	Replaced the invalid environment key with Bun's preload so happy-dom registers for the packages/ui component tests — resolves ReferenceError: document is not defined (6 tests).
Renamed hook	apps/web/src/lib/api.ts	The useSearchDebounce/useThrottle import was stale; the hook is now exported as useDebounce from @e2e/utils. Fixes TS2305 and 2 tests.
Accessibility	packages/ui/.../Button.tsx	Apply aria-label for icon-only buttons, with a dev-only console.warn when it's omitted (accessible-name test).
Stale closure	packages/ui/.../DataTable.tsx	Sort-direction now uses a functional setState updater, removing the captured-render-value dependency (descending-sort test).
Date format	packages/utils/.../date.ts	formatDate emits an unpadded en-AU day via formatToParts (1/03/2024), keeping the month zero-padded and the year 4-digit.

Key decisions & assumptions

• Date format (formatDate): en-AU's Intl silently coerces day: "numeric" to 2-digit, and dateStyle: "short" truncates the year to 2 digits (1/3/24). Chose the formatToParts reassembly so only the single-digit day loses its leading zero — the narrowest change that satisfies the test without regressing the year width for downstream consumers (formatDate is re-exported through api.ts).
• Button aria-label: the test only asserts an accessible name exists, so an icon-only button with no label falls back to "Button" plus a dev warning. A stricter compile-time guard (discriminated-union props) would be a breaking API change and was intentionally left out of scope.
• Remaining tsc output is limited to pre-existing Cannot find module 'bun:test' errors in test files — unchanged from the base commit (confirmed via git stash), and out of scope since fixing them would require editing test files or adding deps.

Constraints honoured

• No test files modified.
• No dependencies added.
• Only the code required by the failing tests was changed.

Verification

• bun test -> 13 pass / 0 fail
• tsc --noEmit -> real TS2305 error eliminated; only the pre-existing bun:test baseline remains.