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/forms/ContactForm.toHtml.test.ts

@@ -63,3 +63,28 @@ describe('ContactForm.toHtml successMessage', () => {
     expect(html).not.toContain('onerror="alert(1)"');
   });
 });
+
+describe('ContactForm.toHtml accessibility (F2.1)', () => {
+  const fields = [
+    { type: 'text' as const, label: 'Name', name: 'name', placeholder: 'Your name', required: true },
+    { type: 'email' as const, label: 'Email', name: 'email', placeholder: 'you@example.com', required: true },
+  ];
+
+  test('each field label for= matches its control id=, and ids are unique', () => {
+    const { html } = toHtml({ fields }, '');
+    const labelIds = [...html.matchAll(/<label for="([^"]+)"/g)].map((m) => m[1]);
+    const controlIds = [...html.matchAll(/<(?:input|textarea|select) id="([^"]+)"/g)].map((m) => m[1]);
+    expect(labelIds.length).toBe(2);
+    expect(controlIds.length).toBe(2);
+    expect(labelIds).toEqual(controlIds);
+    expect(new Set(controlIds).size).toBe(2);
+  });
+
+  test('ids are deterministic across repeated calls with the same fields', () => {
+    const { html: html1 } = toHtml({ fields }, '');
+    const { html: html2 } = toHtml({ fields }, '');
+    const ids1 = [...html1.matchAll(/<input id="([^"]+)"/g)].map((m) => m[1]);
+    const ids2 = [...html2.matchAll(/<input id="([^"]+)"/g)].map((m) => m[1]);
+    expect(ids1).toEqual(ids2);
+  });
+});