feat: dedupe duplicate catalog_pages to prevent double links

The maintenance "Fix alles" now collapses catalog_pages that share the same
caption_save + parent_id into a single survivor (moving catalog_items and
reparenting child pages before deleting duplicates), so the catalog tree
never renders double links. The duplicate-page count is also surfaced in the
health panel.

src/components/admin/catalog/catalog-maintenance-panel.tsx

@@ -31,6 +31,7 @@ interface Health {
 	idMismatchVsFurnidata: number;
 	catalogDuplicates: number;
 	catalogBcDuplicates: number;
+	catalogPageDuplicates: number;
 }
 
 export function CatalogMaintenancePanel() {
@@ -167,6 +168,11 @@ export function CatalogMaintenancePanel() {
 								value={health.catalogBcDuplicates}
 								hint="same product listed twice in builder club"
 							/>
+							<Stat
+								label="Duplicate catalog pages"
+								value={health.catalogPageDuplicates}
+								hint="same caption under the same parent (double links)"
+							/>
 						</>
 					)}
 				</CardContent>