fix: resolve cross-package test failures in monorepo

[stooit]

Summary

Fixes all 5 failing tests and the related type error across the monorepo. After these changes bun run test reports 13 pass / 0 fail and npx tsc --noEmit has no new errors (only pre-existing bun:test resolution noise in untouched test files remains).

Bugs fixed

1. Renamed hook (cross-package) — apps/web/src/lib/api.ts imported useThrottle from @e2e/utils, which no longer exists. Updated to import the actual export useDebounce and re-export it under the consumer-facing name useSearchDebounce that the test expects.
2. Button accessibility — icon-only Button now forwards aria-label to the underlying <button> so it has an accessible name, and emits a console.warn when an icon-only button is rendered without one.
3. Date formatting — packages/utils/src/format/date.ts produced a locale-dependent string. Now builds a deterministic DD/MM/YYYY value so the day is not confused with the month.

Verification

• bun run test → 13 pass / 0 fail
• npx tsc --noEmit → no new errors (pre-existing bun:test test-file errors are unchanged and out of scope)
• The pre-existing DataTable stale-closure test still passes — unaffected by these changes.

Assumptions / scope

• Followed constraints: no test files modified, no dependencies added, fixed only what the tests require.
• The canonical exported hook name was fixed as useSearchDebounce per the test; api.ts was reconciled to that.

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