feat(static-pages): navigation integration (insert page link)

Milestone 6 of the Static Pages Module sprint.

- ProjectEditorFacade.addStaticPageNavLink(target, pageId): creates a
  NavigationItemConfig { type: 'staticPage', key: pageId }. This shape was
  already understood end-to-end by the resolvers (StaticPageResolverService/
  FooterResolverService derive label+route from the linked page - see
  footer-resolver.service.ts resolveGroupItem/resolveLegacyItem) - the only
  gap was that the editor UI never exposed a way to create it.
- navigation-section: "Insert page link" control (page picker + button) next
  to both header and footer "Add link". Rows for a static-page link show a
  "Linked to page" indicator instead of the raw label/URL inputs (those
  fields don't apply - the resolver derives them dynamically). labelOf()
  falls back to the page id for the row heading since a static-page link has
  no label of its own.
- i18n: builder.insertPageLink, builder.linkedToPage in interface + en/ru/hy.

Verified (no rebuild needed) that pages already participate in preview(),
exportBootstrap()/importBootstrap(), and draft/publish gating - all flow
through bootstrap.staticPages and the M1-M2 additive fields untouched here.

Gate: tsc --noEmit, npm test (57/57), arch:check, build all green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/features/project-editor/facade/project-editor.facade.ts

@@ -386,6 +386,31 @@ export class ProjectEditorFacade {
     return true;
   }
 
+  /**
+   * Inserts a nav link that points at a static page by id rather than a raw
+   * route. `type: 'staticPage'` is already understood by the resolvers
+   * (StaticPageResolverService / FooterResolverService derive the label and
+   * route from the page itself) - this only closes the editor-side gap of
+   * never being able to create that item shape.
+   */
+  addStaticPageNavLink(target: 'header' | 'footer', pageId: string): void {
+    this.updateBootstrap(current => {
+      const list = current.navigation[target];
+      if (!this.isFlatNavList(list) || !pageId) {
+        return current;
+      }
+      const items = list as NavigationItemConfig[];
+      const newItem: NavigationItemConfig = {
+        id: `nav-page-${Date.now()}`,
+        type: 'staticPage',
+        key: pageId,
+        order: items.length + 1,
+        visible: true,
+      };
+      return { ...current, navigation: { ...current.navigation, [target]: [...items, newItem] } };
+    });
+  }
+
   addNavLink(target: 'header' | 'footer'): void {
     this.updateBootstrap(current => {
       const list = current.navigation[target];