feat(builder): implement visual homepage builder

New HomepageOverviewComponent (Tasks 1+8), mounted at the top of the
existing Homepage section page: completion ring, active/hidden section
counts, recommended next step, last-modified timestamp, and a 6-item
Homepage Health checklist (hero/categories/products/promotion/
newsletter/any-sections) - all derived from the real page.sections/
widgets data already in the facade, nothing fabricated.

Existing page-level drag-and-drop reordering (homepage-section's
CdkDragDrop over page.sections) was already implemented pre-Sprint 5 -
left as-is per "build on top of, do not replace."

Widgets section (Task 2) rewritten from a bare list into visual cards:
per-widget icon + humanized type label (hero/categories/product-
collection), a visible/hidden toggle and badge, up/down move buttons
(keyboard-accessible reorder within a section - see Known limitations
for why this replaces pointer drag for widgets specifically), duplicate,
and remove (with confirm). The existing per-type field editors (hero/
categories/product-collection) are unchanged; the raw-JSON fallback for
unknown widget types now sits behind a collapsed "Advanced settings"
disclosure instead of being the default view.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/features/project-editor/sections/homepage-section.component.html

@@ -1,4 +1,5 @@
 @if (homePage()) {
+<app-homepage-overview />
 <app-section-card [title]="'builder.homepage' | translate">
   @if (fieldError('pages'); as msg) {
     <p class="editor-error">{{ msg }}</p>