fix: repair cross-package test failures and clean type errors

[stooit]

Summary

Fixes all failing tests and eliminates all type errors across the monorepo. Baseline was 8 pass / 5 fail plus a tsc error; now 13 pass / 0 fail and npx tsc --noEmit exits 0 with no output.

Changes

• apps/web/src/lib/api.ts — the useThrottle hook was renamed to useDebounce in packages/utils, but the app still imported the old name (TS2305). Updated the import to useDebounce and re-exported it as useSearchDebounce (which the api test asserts). Merged the two duplicate @e2e/utils imports.
• packages/ui/src/components/Button/Button.tsx — iconOnly buttons never applied aria-label, leaving them with no accessible name (WCAG 2.2 SC 4.1.2). Now applies aria-label with a fallback chain: explicit label → string children → "Button", so an icon-only button always has a non-null accessible name.
• packages/utils/src/format/date.ts — formatDate emitted a zero-padded day (01/03/2024); the test expects an unpadded day (1/03/2024). Reimplemented with Intl.DateTimeFormat.formatToParts under en-AU, producing an unpadded day while keeping a 4-digit year. (Ordering was never the bug — Intl ignores option order; the failing assertion was day padding.)
• tsconfig.json — added "types": ["bun-types"] so bun:test resolves under tsc --noEmit (the 4 remaining bun:test TS2307 errors). bun-types was already installed; it just wasn't registered. Verified @types/react still resolves via the module import graph, so nothing regressed.

Verification

• bun run test → 13 pass / 0 fail
• npx tsc --noEmit → exit 0, clean

Constraints honoured

• No test files modified.
• No dependencies added (package.json / lockfile untouched).
• Fixed only what the tests require.

Assumptions & decisions

• Date format: chose formatToParts over dateStyle: "short" to keep an unambiguous 4-digit year (1/03/2024) rather than 1/3/24; both would pass the test.
• Button dev-warning removed: an earlier draft added a process.env.NODE_ENV dev-console.warn to Button. Since packages/ui ships as raw source (main → ./src/index.ts), process may be undefined in a browser bundler → ReferenceError at render. No test required it, so it was removed as a latent hazard.
• aria-hidden on the icon not added: would have created a nameless-button regression for <Button icon /> used without iconOnly (the fallback is gated on iconOnly). Left the icon wrapper unchanged.

Known-remaining (out of scope — tests pass, not touched)

• DataTable.tsx carries a documented stale-closure bug in handleSort, but its tests pass — left untouched per "fix only what tests require". Worth a follow-up issue.
• formatDate depends on the ambient timezone; adding timeZone: "UTC" was avoided since it would render wrong dates for real AU users. Tests are stable across UTC/Sydney/Perth.