feat(builder): nav/menu link-to-page picker, page sync, download attr, box-model rollout

NavStylePanel (Navbar/Menu/Logo/Footer):
- LinkPicker: dropdown of the site's pages (read-only via usePages()) plus
  manual URL / #anchor / tel: / mailto: entry, wired into every link-href
  field (standalone Logo href, Navbar logoUrl, Navbar/Menu link items).
- "Sync links with Pages" button in the Links section: repopulates the
  links array from the current pages list (label = page name, href = '/'
  for the landing page else '/{slug}'), preserving any existing CTA link.
  Regression-fix vs the legacy GrapesJS builder, which had this.
- `download` checkbox per link (Navbar/Menu links, standalone Logo href)
  emits the `download` attribute on export for links to files.
- Links/Colors sections now gate on the component actually carrying a
  `links`/color prop, so Footer (no links array) no longer shows a dead
  "Add Link" editor.
- Box-model (Margin/Padding via SpacingControl, Border & Effects via
  BorderControl + box-shadow presets + opacity), AnimationControl, and
  VisibilityControl added for all four owned components, backed by new
  animation/animationDelay/hideOnDesktop/hideOnTablet/hideOnMobile props
  (with blank/default values in each component's .craft.props).

Tests: NavStylePanel.test.tsx (new, 17 tests: LinkPicker modes, sync
preserves CTA, download toggle, box-model/animation/visibility wiring) +
extended Navbar/Menu/Logo/Footer .toHtml.test.ts (download attribute,
craft.props defaults). Full suite: 683/683 passing. `npm run build` green.

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

craft/src/components/basic/Footer.toHtml.test.ts

@@ -20,3 +20,14 @@ describe('Footer.toHtml text escaping (attacker-controlled `text` prop)', () =>
     expect(html).toContain('© 2026 MySite. All rights reserved.');
   });
 });
+
+describe('Footer (F4: box-model + animation + visibility props on craft.props)', () => {
+  test('craft.props includes animation/visibility defaults so the panel controls always render', () => {
+    const craftProps = (Footer as any).craft.props;
+    expect(craftProps).toHaveProperty('animation', 'none');
+    expect(craftProps).toHaveProperty('animationDelay', '0');
+    expect(craftProps).toHaveProperty('hideOnDesktop', false);
+    expect(craftProps).toHaveProperty('hideOnTablet', false);
+    expect(craftProps).toHaveProperty('hideOnMobile', false);
+  });
+});