fix: repair failing tests and type errors across the monorepo

[stooit]

Summary

Fixes all failing tests and eliminates all type errors in the monorepo. bun test now reports 13 pass / 0 fail and tsc --noEmit exits clean.

Six root causes across three packages, plus one test-config cleanup:

File	Fix	Bug
apps/web/src/lib/api.ts	useThrottle → useDebounce (public useSearchDebounce name preserved)	Stale import of a renamed hook — @e2e/utils no longer exported the old name
bunfig.toml	Replaced unsupported environment = "happy-dom" key with preload = ["./packages/ui/test/setup.ts"]	document is not defined — happy-dom was never actually registered, so all React Testing Library render() calls crashed
tsconfig.json	Added "types": ["bun-types"]	Cannot find module 'bun:test' under tsc --noEmit
packages/utils/src/format/date.ts	en-AU → en-GB (day:"numeric", month:"2-digit")	en-AU silently upgrades day:"numeric" to 2-digit, producing 01/03/2024; test expects 1/03/2024
packages/ui/.../Button.tsx	Apply aria-label for icon-only buttons (string-child derivation, honest "icon button" fallback, dev-time warning) [WCAG 2.2 SC 4.1.2]	Icon-only button had no accessible name
packages/ui/.../DataTable.tsx	Functional setSortDir(prev => ...) in the sort handler	Robustness fix — see assumption below
package.json	Dropped the duplicate --preload flag now covered by bunfig.toml	Avoided double GlobalRegistrator.register()

Verification

• bun test from repo root: 13/13 pass
• bun run test (npm script): 13/13 pass
• bunx tsc --noEmit: clean (exit 0)

Assumptions & notes

• No test files were modified and no dependencies were added (happy-dom and bun-types were already in devDependencies).
• DataTable "stale closure": investigation found the sort handler was not actually stale — handleSort is recreated each render, so those tests were red purely because of the happy-dom setup, not a closure bug. The functional-setState change is retained as a defensive, idiomatic improvement (no behaviour change, no regression), but it was not strictly required by the tests.
• Button accessible name: the test only asserts the aria-label is non-null, and test files cannot be changed, so a synthesised fallback is unavoidable. The fallback is an honest "icon button" and a dev-time console.warn nudges developers to supply a real label. Consider promoting that warning to a hard error in CI in a follow-up so meaningless names can't ship silently.
• date.ts locale: en-GB was chosen to satisfy the day-first / no-leading-zero assertion. An en-AU-preserving alternative (dateStyle: "short") also passes but changes the year to 2 digits; formatDateTime was intentionally left on en-AU to avoid scope creep beyond what the tests require.