fix(z-input): add aria-required to required checkboxes

[ada-workbackai]

Summary

Fixes WCAG 1.3.1 (Info and Relationships) by ensuring checkbox inputs programmatically indicate their required status through the aria-required attribute.

Issue: Required checkboxes in the registration form lack programmatic indicators of their required status. Screen reader users cannot determine which checkboxes are mandatory, forcing them to use trial-and-error to discover form requirements.

Solution: Modified the z-input component to automatically add aria-required="true" when the required prop is set on checkbox inputs. This ensures both the HTML5 required attribute and ARIA aria-required attribute are present for maximum accessibility compatibility.

Changes

• src/components/z-input/index.tsx: Added aria-required="true" to checkbox inputs when required prop is true
• src/components/z-input/test-checkbox.spec.ts: Added unit test verifying aria-required is applied to required checkboxes

Test Plan

• Added unit test for required checkbox with aria-required attribute
• Verified existing checkbox tests still pass
• Manually tested with screen reader (VoiceOver/NVDA) to confirm required status is announced
• Verified visual appearance is unchanged

Impact

This fix applies to all checkboxes rendered with <z-input type="checkbox" required> across all applications using the design system, including:

• Registration forms (student, teacher, professional)
• Consent forms
• Any other forms with required checkbox fields

Evidence

View before/after screenshots and full audit details:
https://app.workback.ai/dashboard/issue/5054/

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WCAG Reference:
1.3.1 Info and Relationships