fix: resolve all failing tests and type errors across monorepo

[stooit]

Summary

Fixes all 5 failing tests and eliminates all TypeScript errors across the packages/ui, packages/utils, and apps/web workspaces. bun run test → 13 pass / 0 fail and tsc --noEmit → clean.

Root causes & fixes

Package	File	Bug	Fix
utils→web	apps/web/src/lib/api.ts	Imported/re-exported the old hook name useThrottle, which no longer exists (TS2305)	Point the import + re-export at the real export useDebounce; the app-facing useSearchDebounce alias is preserved
ui	packages/ui/src/components/Button/Button.tsx	aria-label was declared in Props but never applied, so icon-only buttons had no accessible name	Apply aria-label with a fallback for iconOnly, plus a dev-only warning when an icon-only button is unlabelled (WCAG 2.2 SC 4.1.2)
ui	packages/ui/src/components/DataTable/DataTable.tsx	Sort-direction toggle read stale state in its closure (caught by the controlled re-render test)	Use functional setSortDir(prev => …)
utils	packages/utils/src/format/date.ts	formatDate zero-padded the day (01/03/2024), failing the /^1/ assertion	Emit day-first D/MM/YYYY with no leading zero on the day
build	tsconfig.json	bun:test unresolved under tsc (4× TS2307)	Add "types": ["bun-types"] (already a devDependency)

Verification

$ bun run test   → 13 pass / 0 fail
$ tsc --noEmit   → 0 errors

Constraints honoured

• No test files modified.
• No dependencies added (bun-types was already a devDependency).
• Each edit maps to a specific failing test / type error.

Assumptions & notes for reviewers

• The real defect in formatDate was day zero-padding, not field order — the original already emitted day-first. The fix targets the padding only.
• The Button aria-label prop now also flows through to text buttons (previously inert). No test exercises that path; flagged as a WCAG 2.5.3 follow-up, not changed here since no test requires it.
• Pre-existing, out of scope (no regression, not test-required): formatDate has no timeZone option so it renders in system TZ; and DataTable's sort control is a click handler on a non-focusable <th> (keyboard operability, WCAG 2.1.1). Both worth follow-up tickets.

Investigation plan retained at docs/plans/2026-08-01-fix-5-failing-tests-and-tsc-error.md.