fix: resolve cross-package test failures in monorepo

[stooit]

Summary

Fixes all 5 failing tests and the real type error across the monorepo. Baseline was 8 pass / 5 fail with one tsc error; now 13 pass / 0 fail and tsc clean.

Three bugs, spanning all three packages:

• apps/web/src/lib/api.ts (hook rename mismatch). The app imported useThrottle from @e2e/utils, which no longer exists (tsc: Module @e2e/utils has no exported member useThrottle). The real export is useDebounce (trailing-edge debounce). Aligned the app import to useDebounce, aliased as useSearchDebounce — the name the test expects — without changing the hook's true semantics or renaming anything in a test file.
• packages/ui/src/components/Button/Button.tsx (missing a11y attribute). Icon-only buttons rendered no accessible name. Added aria-label wiring so an icon-only button always exposes a non-null accessible name (WCAG 4.1.2), passing through a caller-supplied label verbatim.
• packages/utils/src/format/date.ts (locale/format). formatDate(1 March 2024) returned zero-padded 01/03/2024; the test requires a day-first, non-padded leading day (/^1/). Switched to locale-aware en-AU formatting so it renders 1/03/2024.

The DataTable "sorts descending on second click" (stale-closure) test was verified to already pass — no change needed there.

Verification

• bun run test -> 13 pass, 0 fail
• ./node_modules/.bin/tsc --noEmit -> clean apart from pre-existing Cannot find module 'bun:test' errors in test files (present before this change; test-typing environment quirk, out of scope)

Constraints honoured

• No test files modified
• No dependencies added
• Only the three source files above changed

Assumptions / notes for reviewers

• Button fallback: when an icon-only button is given no children and no label, it falls back to aria-label="Button" to satisfy the test's not.toBeNull() assertion. This is a weak label; the cleaner long-term fix is a type-level requirement that iconOnly demands an aria-label, but that would require amending Button.test.tsx, which the task forbids.
• Date presentation: formatDate uses day: numeric / month: 2-digit / 4-digit year to satisfy the test while keeping the full year; note formatDateTime in the same module uses a shorter style, so the two are not visually identical. Left as-is since no test requires alignment.
• Pre-existing, out of scope: DataTable sort headers (<th onClick>) are not keyboard-operable (WCAG 2.1.1); a shared date util hardcodes en-AU with no explicit timeZone. Neither is introduced here and neither is covered by a failing test.