Add customergroup sort with bulk order and locked implicit names.

Reorder via customergroup.order (exact id list → sort 0…n-1); block renaming POS/Lieferanten while still allowing create/update of other groups by name.

src/store/supplier/ensureLieferantenGroup.js

@@ -1,6 +1,7 @@
 import {
   CREATE,
   GET_BY_COMPANY_AND_NAME,
+  GET_NEXT_SORT,
 } from '../../sql/customergroup.js';
 import { SUPPLIER_GROUP_NAME } from '../../sql/entity.js';
 
@@ -17,9 +18,15 @@ export default async function ensureLieferantenGroup(pool, companyId, tx) {
     return existing.recordset[0].id;
   }
 
+  const next = await req()
+    .input('companyId', companyId)
+    .query(GET_NEXT_SORT);
+  const sort = next.recordset[0].sort;
+
   const created = await req()
     .input('companyId', companyId)
     .input('name', SUPPLIER_GROUP_NAME)
+    .input('sort', sort)
     .query(CREATE);
 
   return created.recordset[0].id;