Search input has accessible label; autocomplete uses ARIA live region

A search input without an associated label fails WCAG 2.2 SC 4.1.2 (Name, Role, Value) — screen readers announce the field as "edit text" with no context, making it unusable for blind users. Autocomplete dropdowns that don't use aria-live or role="listbox" are invisible to assistive technology: suggestions appear visually but are never announced, so keyboard and screen reader users cannot benefit from them. WCAG 2.2 SC 4.1.3 (Status Messages) further requires that dynamic content changes like suggestion updates be communicated without requiring focus movement.

Label the search input explicitly and annotate the suggestions container with ARIA roles. In components/SearchInput.tsx:

<label htmlFor="search-input">Search listings</label>
<input
  id="search-input"
  type="text"
  role="combobox"
  aria-expanded={suggestions.length > 0}
  aria-autocomplete="list"
  aria-controls="suggestions-list"
/>
{suggestions.length > 0 && (
  <ul
    id="suggestions-list"
    role="listbox"
    aria-live="polite"
  >
    {suggestions.map((s, i) => (
      <li key={i} role="option">{s.name}</li>
    ))}
  </ul>
)}

aria-live="polite" causes screen readers to announce new suggestions without interrupting the user's current context. Test with VoiceOver (macOS) or NVDA (Windows) to verify announcements fire on each suggestion update.