fix: repair cross-package bugs breaking tests and type checks

[stooit]

Summary

Fixes all failing tests and type errors across the monorepo (bun run test → 13/13 pass; bun run typecheck → clean). Bugs spanned all three packages.

Changes

• packages/utils/src/format/date.ts — formatDate now renders day and month without leading zeros for en-AU (e.g. 1/3/2024), fixing the "day 1 not confused with month 1" test. Uses Intl.DateTimeFormat.formatToParts because Bun's ICU zero-pads numeric day.
• apps/web/src/lib/api.ts — the hook was renamed in packages/utils; updated the import from the non-existent useThrottle to useDebounce and fixed the useSearchDebounce re-export (resolves TS2305 + the api module test).
• packages/ui/src/components/Button/Button.tsx — icon-only buttons now pass through aria-label verbatim, and emit a dev console.warn (WCAG 4.1.2) when an icon-only button is missing an accessible name, matching the test's "should warn" intent.
• packages/ui/src/components/DataTable/DataTable.tsx — fixed a stale-closure bug in the sort-direction toggle by using the functional updater form of setSortDir, caught by the controlled re-render test.
• tsconfig.json — registered bun-types (already installed) so test files resolve bun:test (resolves TS2307).

Verification

• bun run test → 13 pass, 0 fail
• bun run typecheck → 0 errors

Constraints honoured

• No test files modified.
• No dependencies added (bun-types was already present).
• Only the code the tests required was changed.

Assumptions

• The renamed hook is useDebounce (verified as the actual export in packages/utils); useSearchDebounce is the public alias the app/test expects.
• For a missing icon-only aria-label, the test requires a warning (not a placeholder label); implemented as console.warn.
• Day/month rendered unpadded (1/3/2024) as the simplest form satisfying every date assertion.