fix: repair cross-package bugs failing tests and typecheck

[stooit]

Summary

Fixes all failing tests and type errors across the monorepo. bun run test now passes 13/13 and tsc --noEmit exits 0. Five production source files changed; no test files touched, no dependencies added.

Bugs fixed

Package	File	Bug	Fix
apps/web	src/lib/api.ts	Imported useThrottle from @e2e/utils, but the hook was renamed to useDebounce — caused a runtime SyntaxError and TS2305	Import useDebounce; re-export as useSearchDebounce
packages/ui	Button/Button.tsx	Icon-only buttons rendered with no accessible name (WCAG 2.2 SC 4.1.2)	Apply aria-label prop; dev-mode console.warn + "Unlabelled button" fallback when icon-only and no label given
packages/ui	DataTable/DataTable.tsx	Stale-closure sort toggle read sortDir captured at handler-creation time	Use functional setSortDir(prev => ...)
packages/utils	format/date.ts	formatDate zero-padded the day (01/03/2024), failing the day-first assertion	Use Intl.DateTimeFormat en-AU with formatToParts to strip the day's leading zero → 1/03/2024 (keeps 4-digit year, 2-digit month)
root	tsconfig.json	bun:test unresolved (TS2307 x4) because bun-types lives outside @types/*	Add "types": ["bun-types"]

Verification

• bun run test -> 13 pass / 0 fail
• ./node_modules/.bin/tsc --noEmit -> exit 0

Assumptions & decisions

• formatDate: the original code comment misdiagnosed the bug as MM/DD ordering; Intl ignores option declaration order and en-AU is already day-first. The real defect was zero-padding. Chose formatToParts over dateStyle: "short" to preserve a 4-digit year (short style silently truncated to 1/3/24), avoiding a public-API output regression.
• Button aria-label: kept the runtime fallback rather than type-enforcing aria-label for iconOnly — the latter is a breaking API change and would require editing the test file, which is out of scope. Fallback is "Unlabelled button" (not "button") so genuinely unlabelled buttons stay greppable/detectable rather than masking the defect.
• Fixed only what the tests/typecheck require; the DataTable functional-setState change is also a latent-bug hardening.

Out of scope (noted, not changed)

• DataTable sortable <th> elements are mouse-only (no tabIndex/role/onKeyDown) — a pre-existing WCAG 2.2 SC 2.1.1 keyboard-access gap not covered by any test. Worth a separate follow-up.