fix: repair four cross-package bugs surfaced by failing tests

[stooit]

Summary

Fixes all failing tests and the one product-code type error in the monorepo. Four distinct bugs spanning packages/utils, packages/ui, and apps/web:

• apps/web/src/lib/api.ts — the hook useThrottle was renamed to useDebounce in @e2e/utils, but api.ts still imported the old name (the cause of the export 'useSearchDebounce' not found failure and a TS2305 error). Now imports useDebounce and re-exports it under the public alias useSearchDebounce.
• packages/utils/src/format/date.ts — formatDate used explicit { month, day, year: "numeric" } options producing month-first 01/03/2024. Switched to { dateStyle: "short" } with the en-AU locale so dates are day-first (1/03/2024).
• packages/ui/src/components/Button/Button.tsx — the icon-only <button> branch did not forward aria-label, so icon-only buttons had no accessible name. Now forwards aria-label.
• packages/ui/src/components/DataTable/DataTable.tsx — handleSort read stale sortDir from the closure. Switched to the functional state updater setSortDir(prev => ...).

Verification

• bun run test → 13 pass, 0 fail.
• npx tsc --noEmit → the one real product-code error (useThrottle not exported) is gone. The remaining TS2307: Cannot find module 'bun:test' errors are pre-existing (present on the base commit 7e2198e) and confined to test files; the task constraints forbid modifying test files, and they are unrelated to the four bugs.

Notes / assumptions

• No test files were modified and no dependencies were added, per the task constraints.
• dateStyle: "short" was chosen over hand-rolled options because it lets the en-AU locale drive day-first ordering, matching the test's expectation.