fix: repair cross-package bugs so tests and typecheck pass

[stooit]

Summary

Fixes all failing tests and type errors across the monorepo. Final state: 13/13 tests pass, tsc --noEmit clean (exit 0). No test files edited, no dependencies added.

Bugs fixed

1. Renamed hook (apps/web/src/lib/api.ts) — useThrottle was removed from @e2e/utils; the current export is useDebounce. Updated the consumer import (collapsing duplicate @e2e/utils imports) and preserved the public useSearchDebounce name the app test asserts.
2. Button accessibility (packages/ui) — icon-only buttons now pass aria-label through to the <button>, exposing an accessible name (WCAG 2.2 SC 4.1.2). Without a label, a dev-only console.warn fires and a fallback name is applied so the accessible name is never null.
3. DataTable sort (packages/ui) — consolidated sort key and direction into a single SortState object updated functionally, making toggle behaviour robust and internally consistent.
4. formatDate (packages/utils) — emits a day-first Australian date with no leading zero on the day (e.g. 1/03/2024, 15/06/2024) via Intl.DateTimeFormat + formatToParts, matching the test expectations.

Supporting change

• Added packages/utils/test/bun-types.d.ts — a /// <reference types="bun-types" /> shim scoped to the test tree so tsc resolves bun:test for all four test files. Placed under test/ (not src/) so Bun runtime globals do not leak into library/app source. This is a new type-reference file, not a test file.

Assumptions

• The bunfig.toml/setup files are correct; the DOM environment initialises via the repo's test script preload (bun run test), the canonical invocation, which passes fully.
• For bug 1, the intended fix was to update the consumer to the current export name rather than re-add the old hook (no test references useThrottle).
• For bug 4, the day-first / no-leading-zero output is dictated by the test regex; en-AU pads the day even with day: "numeric", so the day is normalised via formatToParts while the locale still controls field order and separators.

Verification

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