a11y: exported semantics (forms/rating/nav/iframe/icons)

- InputField/TextareaField/ContactForm: every control gets a
  deterministic id (slugId() in utils/escape.ts, derived from the
  field's name/label + index for ContactForm's looped fields -- no
  Math.random) with a matching <label for=>; fields with no visible
  label get an aria-label from the placeholder/name instead.
- StarRating: wrapped in role="img" aria-label="Rating: N out of M",
  individual star glyphs marked aria-hidden.
- Navbar: the mobile hamburger toggle gets aria-label="Toggle
  navigation menu", aria-controls="navbar-links", and aria-expanded
  wired to flip true/false in the inline onclick handler.
- VideoBlock and MapEmbed: every exported <iframe> gets a title
  (generic "Embedded video", or "Map of {address}" for MapEmbed).
- Decorative Font Awesome icons (ContentSlider arrows already covered
  in the prior commit; SocialLinks, SearchBar, Testimonials stars) are
  aria-hidden; SocialLinks' icon-only links get an aria-label naming
  the platform alongside the existing title tooltip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

craft/src/components/media/MapEmbed.tsx

@@ -93,6 +93,6 @@ MapEmbed.craft = {
   const src = buildMapUrl(address, zoom);
 
   return {
-    html: `<div${wrapperStyle ? ` style="${wrapperStyle}"` : ''}><iframe src="${escapeAttr(safeUrl(src))}" loading="lazy" referrerpolicy="no-referrer-when-downgrade" allowfullscreen${iframeStyle ? ` style="${iframeStyle}"` : ''}></iframe></div>`,
+    html: `<div${wrapperStyle ? ` style="${wrapperStyle}"` : ''}><iframe src="${escapeAttr(safeUrl(src))}" title="${escapeAttr(`Map of ${address}`)}" loading="lazy" referrerpolicy="no-referrer-when-downgrade" allowfullscreen${iframeStyle ? ` style="${iframeStyle}"` : ''}></iframe></div>`,
   };
 };