Add customergroup bulk reorder and list editable flag.

Expose PUT /customergroup/order for exact-set sort updates, keep create/update name-only, and mark POS/Lieferanten as non-editable in list responses.

src/db/customergroup.js

@@ -15,6 +15,11 @@ export async function update(googleAuthId, companyId, id, data) {
     return store.customergroup.update(googleAuthId, companyId, id, data);
 }
 
+export async function order(googleAuthId, companyId, data) {
+    const store = await getStore();
+    return store.customergroup.order(googleAuthId, companyId, data);
+}
+
 export async function remove(googleAuthId, companyId, id) {
     const store = await getStore();
     return store.customergroup.delete(googleAuthId, companyId, id);