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/TextareaField.toHtml.test.ts

@@ -0,0 +1,21 @@
+import { describe, test, expect } from 'vitest';
+import { TextareaField } from './TextareaField';
+
+const toHtml = (TextareaField as any).toHtml;
+
+describe('TextareaField.toHtml accessibility (F2.1)', () => {
+  test('label for= matches textarea id=', () => {
+    const { html } = toHtml({ label: 'Message', name: 'message' }, '');
+    const forMatch = html.match(/<label for="([^"]+)"/);
+    const idMatch = html.match(/<textarea id="([^"]+)"/);
+    expect(forMatch).toBeTruthy();
+    expect(idMatch).toBeTruthy();
+    expect(forMatch![1]).toBe(idMatch![1]);
+  });
+
+  test('no visible label: textarea gets aria-label from placeholder', () => {
+    const { html } = toHtml({ label: '', name: 'notes', placeholder: 'Anything else?' }, '');
+    expect(html).not.toContain('<label');
+    expect(html).toContain('aria-label="Anything else?"');
+  });
+});