fix: repair cross-package bugs and DOM test wiring

[stooit]

Summary

Fixes all 9 failing tests and 5 tsc --noEmit errors across the monorepo. 13 pass / 0 fail, typecheck clean. No test files modified, no dependencies added.

Root causes & fixes

• apps/web/src/lib/api.ts — imported useThrottle from @e2e/utils, but the hook was renamed to useDebounce. Updated the import while preserving the as useSearchDebounce re-export the api test asserts.
• packages/ui/.../Button.tsx — icon-only buttons had no accessible name. Now applies aria-label, with a dev-only console.warn and a fallback label for unlabelled icon-only buttons (WCAG 2.2 SC 4.1.2). Text buttons keep pass-through behaviour so their accessible name still derives from visible text.
• packages/ui/.../DataTable.tsx — sort-direction toggle read stale state from a closure. Switched to functional setState(prev => ...).
• packages/utils/src/format/date.ts — en-AU numeric format zero-padded the day (01/03/2024), failing the /^1/ assertion. Reassembled via Intl.DateTimeFormat.formatToParts to drop the day's leading zero (1/03/2024).
• bunfig.toml — added preload = ["./packages/ui/test/setup.ts"]. bun test at the repo root resolves bunfig.toml from CWD only and never reads the per-package bunfig, so happy-dom's global-registrator wasn't running — causing the document is not defined failures. This is the wiring change that fixed 6 of the 9 failures.
• tsconfig.json — added "types": ["bun-types"] (already-installed dep) so bun:test resolves, clearing the 4 TS2307 errors.

Verification

• bun test (bare, from root): 13 pass / 0 fail, verified stable across repeated runs
• npx tsc --noEmit: exit 0, clean
• Per-package runs (ui / utils / web) all green

Assumptions & notes

• The DataTable stale-closure fix is not strictly required by the test (it passes without it once the DOM exists, since fireEvent.click flushes re-renders), but it is a genuine latent bug and the functional-setState form is strictly more correct — kept as a zero-risk correctness fix.
• The date.ts and Button.tsx in-code BUG: comments were misdiagnosing the actual causes; docblocks were updated to match the real fixes.
• Follow-up (out of scope): the icon-only fallback label satisfies SC 4.1.2 in the letter but isn't descriptive. The cleaner design makes aria-label a required prop when iconOnly — a breaking Props API change that would conflict with the current test contract.

Constraints honoured

• No test files modified
• No new dependencies added
• Fixed only what the failing tests required (plus the one zero-risk latent DataTable bug)