fix: resolve failing tests and type errors across monorepo - #292

Summary

bun test && tsc --noEmit now passes: 13 of 13 tests pass and tsc reports no errors.

• Test env: bunfig.toml had an invalid environment = "happy-dom". It now preloads packages/ui/test/setup.ts, which registers the already-installed @happy-dom/global-registrator.
• Types: added "types": ["bun-types"] to the root tsconfig.json (the package is already a devDependency).
• apps/web: api.ts imported useThrottle, which was renamed in @e2e/utils. It now imports useDebounce.
• ui/DataTable: the sort toggle now uses a functional setSortDir(prev => ...) update, which fixes the stale-closure bug.
• ui/Button: the aria-label prop is now applied to the button. Icon-only buttons without a label fall back to "Button" and log a console.warn outside production.
• utils/formatDate: output is now D/MM/YYYY via formatToParts, in local time (consistent with formatDateTime).

Assumptions

• I didn't change any test files or add dependencies.
• The "Button" fallback label is only there to satisfy the test. Callers should still pass a real label. Making the prop required for icon-only buttons would break the existing test's typecheck, so I left the type as it is.
• formatDate uses local time rather than UTC, so dates aren't shifted in AU timezones. The tests use 12:00Z dates, so they pass everywhere except near ±12h.
• A stale // BUG: comment is still in packages/ui/test/DataTable.test.tsx:43. I left it because test files are off-limits.

Review

I had the change reviewed, applied the two high findings, and the re-review approved it.