feat(builder): visual footer builder with drag-and-drop columns

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

P0 user feedback: footer static pages were comma-separated text; no way to add extra phones/emails for different countries.

- New FooterColumnConfig/FooterLinkConfig model (footer-config.model.ts): columns of links, each link pointing at an existing static page (resolved by key, so it survives route renames) or a custom URL
- Footer Builder UI: add/remove columns and links, per-link toggle between 'existing page' (dropdown of real static pages) and 'custom URL', drag-and-drop reordering of both columns and links via @angular/cdk/drag-drop (same primitive already used by the homepage section builder)
- Wired FooterResolverService (the service the real storefront footer actually renders through) to read footer.columns as the primary source when present - without this the builder would have saved data nobody ever displayed. Falls back to the existing legacy static-page auto-grouping when no columns are configured, so existing sites are unaffected
- CompanyContactConfig gains additionalPhones/additionalEmails (primary phone/email field unchanged) with add/remove UI for country-specific support lines
- Old comma-separated staticPageKeys input removed from the UI; field kept on the model as deprecated/read-compat only
- New builder.* i18n keys (en/ru/hy); fixed an accidental duplicate-key collision with pre-existing navigation-section addLink/removeLink keys during the rename pass
- Verified in browser: added column, added link, switched link source page->custom, added phone number - all reactive and error-free

src/app/features/project-editor/sections/footer-section.component.scss

@@ -0,0 +1,96 @@
+.contact-row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  margin-bottom: 6px;
+
+  app-input { flex: 1; }
+}
+
+.contact-row__remove {
+  border: none;
+  background: transparent;
+  cursor: pointer;
+  color: var(--text-secondary, #6b7280);
+  font-size: 1rem;
+
+  &:hover { color: var(--danger-color, #c0392b); }
+}
+
+.footer-columns {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 12px;
+  margin: 8px 0;
+}
+
+.footer-column {
+  display: grid;
+  gap: 8px;
+  width: 260px;
+  padding: 10px;
+  border: 1px solid var(--border-color, #d3dad9);
+  border-radius: var(--radius-sm);
+  background: var(--bg-secondary, #f7f8f8);
+
+  &.cdk-drag-preview { box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15); }
+  &.cdk-drag-placeholder { opacity: 0.4; }
+}
+
+.footer-column__head {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+
+  app-input { flex: 1; }
+}
+
+.footer-column__grip { cursor: grab; color: var(--text-secondary, #6b7280); }
+
+.footer-column__remove {
+  border: none;
+  background: transparent;
+  cursor: pointer;
+  color: var(--text-secondary, #6b7280);
+  font-size: 1rem;
+
+  &:hover { color: var(--danger-color, #c0392b); }
+}
+
+.footer-column__links {
+  display: grid;
+  gap: 6px;
+  min-height: 20px;
+}
+
+.footer-link {
+  display: grid;
+  grid-template-columns: auto 1fr auto;
+  grid-template-areas:
+    "grip label remove"
+    "source source source"
+    "target target target";
+  gap: 4px 6px;
+  align-items: center;
+  padding: 6px;
+  border: 1px solid var(--border-color, #d3dad9);
+  border-radius: var(--radius-sm);
+  background: #fff;
+
+  &.cdk-drag-preview { box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15); }
+  &.cdk-drag-placeholder { opacity: 0.4; }
+}
+
+.footer-link__grip { grid-area: grip; cursor: grab; color: var(--text-secondary, #6b7280); }
+.footer-link app-input:first-of-type { grid-area: label; }
+.footer-link__remove {
+  grid-area: remove;
+  border: none;
+  background: transparent;
+  cursor: pointer;
+  color: var(--text-secondary, #6b7280);
+}
+.footer-link__source { grid-area: source; }
+.footer-link app-input[type="url"], .footer-link select:not(.footer-link__source) { grid-area: target; }
+
+.cdk-drag-animating { transition: transform 200ms cubic-bezier(0, 0, 0.2, 1); }