fix: repair cross-package test and type failures

[stooit]

Summary

Fixes all failing tests and type errors across the monorepo. bun test → 13 pass, 0 fail; tsc --noEmit → exit 0, no errors.

Root causes & fixes

1. apps/web/src/lib/api.ts — Hook was renamed useThrottle → useDebounce in packages/utils, but the old name was still imported/re-exported. Updated the import and the useSearchDebounce re-export.
2. packages/utils/src/format/date.ts — formatDate produced a leading-zero day (01/03/2024). Rewrote to output DD/MM/YYYY with unpadded day and zero-padded month (1/03/2024), using UTC accessors.
3. bunfig.toml — Component tests failed with document is not defined from the repo root because the happy-dom setup wasn't preloaded. Added preload of the UI test setup.
4. packages/ui/src/components/Button/Button.tsx — Icon-only buttons never applied an accessible name. Now always applies aria-label.
5. packages/ui/src/components/DataTable/DataTable.tsx — Stale-closure bug in the sort toggle. Switched to a functional state updater so a second click toggles to descending.
6. tsconfig.json — Added bun-types to compilerOptions.types (already installed) so bun:test resolves, and included app sources. Resolves the 4 pre-existing Cannot find module 'bun:test' errors.

Verification

• bun test: 13 pass, 0 fail
• node_modules/.bin/tsc --noEmit: exit 0

Constraints honoured

• No test files modified. No dependencies added (bun-types already present). Changes minimal, root-cause fixes, independently reviewed.

Assumptions

• The useThrottle → useDebounce rename is intentional; the fix updates consumers rather than restoring the old export.
• formatDate is expected to be UTC-based / locale-independent (matches all date-test assertions).