fix: repair 4 cross-package bugs to make test suite pass

[stooit]

Summary

Fixes all failing tests in the monorepo. Suite went from 8 pass / 5 fail → 13 pass / 0 fail. The only source type error (useThrottle TS2305) is resolved.

Four cross-package bugs, one per hinted area:

Area	File	Fix
Renamed hook	apps/web/src/lib/api.ts	Import useDebounce and re-export as useSearchDebounce; repaired the useThrottle import so @e2e/utils exposes the names api.ts consumes. Merged duplicate @e2e/utils imports.
Accessibility	packages/ui/src/components/Button/Button.tsx	Forward aria-label to the rendered <button> for icon-only buttons (WCAG 2.2 SC 4.1.2).
Stale closure	packages/ui/src/components/DataTable/DataTable.tsx	Use functional setState in the sort handler to avoid a latent stale-closure across controlled re-renders.
Date format	packages/utils/src/format/date.ts	Strip zero-padding from the day (day-first, month stays padded).

Verification

• bun test packages/utils/test packages/ui/test apps/web/test --preload ./packages/ui/test/setup.ts → 13 pass / 0 fail
• npx tsc --noEmit → only 4 pre-existing Cannot find module 'bun:test' errors, all in untouched test files (verified against a stash at HEAD). Resolving those would need bun-types / a tsconfig edit — out of scope under the no-new-deps / no-test-edits constraints.

Assumptions & constraints honoured

• No test files modified; no dependencies added.
• Date fix matches the test's /^1/ expectation (non-padded day-first) without altering month padding.
• DataTable functional-setState change is semantically equivalent for passing paths — hardening against the stale-closure the re-render test exercises.
• Reviewed via the review subagent: approved, no blockers.