feat: catalog audit can repair orphaned refs and duplicate classnames

- add repairOrphanedCatalog: remove catalog_items rows whose item_ids only
  reference missing items_base entries, strip orphaned ids from mixed rows
- add repairDuplicateClassnames: merge items_base duplicates into one
  canonical row per classname, remap references, delete duplicate rows
- add 'repair structural issues' checkbox + result display in audit UI

src/app/api/admin/import/audit/route.ts

@@ -16,6 +16,7 @@ export const POST = withAdmin(
 		let sql = false;
 		let applySql = false;
 		let repairFurniData = false;
+		let repairStructure = false;
 		try {
 			const body = (await request.json().catch(() => ({}))) as {
 				repair?: unknown;
@@ -23,12 +24,14 @@ export const POST = withAdmin(
 				sql?: unknown;
 				applySql?: unknown;
 				repairFurniData?: unknown;
+				repairStructure?: unknown;
 			};
 			repair = body.repair === true;
 			repairNitros = body.repairNitros === true;
 			sql = body.sql === true;
 			applySql = body.applySql === true;
 			repairFurniData = body.repairFurniData === true;
+			repairStructure = body.repairStructure === true;
 		} catch {
 			/* no body */
 		}
@@ -50,6 +53,7 @@ export const POST = withAdmin(
 						sql,
 						applySql,
 						repairFurniData,
+						repairStructure,
 					});
 				} catch (err) {
 					send({