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.tsx

@@ -6,6 +6,11 @@ import { escapeHtml } from '../../utils/escape';
 interface FooterProps {
   text?: string;
   style?: CSSProperties;
+  hideOnDesktop?: boolean;
+  hideOnTablet?: boolean;
+  hideOnMobile?: boolean;
+  animation?: string;
+  animationDelay?: string;
 }
 
 export const Footer: UserComponent<FooterProps> = ({
@@ -92,6 +97,11 @@ Footer.craft = {
       fontSize: '14px',
       padding: '24px 20px',
     },
+    hideOnDesktop: false,
+    hideOnTablet: false,
+    hideOnMobile: false,
+    animation: 'none',
+    animationDelay: '0',
   },
   rules: {
     canDrag: () => true,