[Sammyzyandev]

Summary

• Expose CurrencyInput as a named spinbutton with its current Naira value and applicable minimum/maximum.
• Mark validation errors as assertive live updates while preserving the visible keyboard focus ring.
• Add coverage for the input's accessible name, bounds, error announcement, and axe checks.

Validation

• npm test -- --runInBand components/CurrencyInput.test.tsx — passed (8 tests), including axe.
• npm run lint (TypeScript check) reports existing failures in unrelated metadata, formatting, and config files; no CurrencyInput errors were reported.
• git diff --check and full added-line PolinRider scan — passed.

Closes #457