Add proper modal ARIA attributes

[Mosas2000]

Description

Modal components lack proper role="dialog" and aria-modal="true" attributes.

Affected Components

• ShareModal.tsx
• MobileBottomSheet.tsx

Impact

• Violates WCAG 2.1 Level A (4.1.2 Name, Role, Value)
• Screen readers may not announce modal state correctly

Solution

<div role="dialog" aria-modal="true" aria-labelledby="modal-title">
  <h2 id="modal-title">Modal Title</h2>
  {/* content */}
</div>

Priority

♿ MEDIUM - Accessibility compliance