fix: import ScanCommand, which had been failing every deploy since 08-27

listAllMachines reached for ScanCommand without importing it, so the backend
type check failed in CI and took the whole build down with it. Production has
been stuck on d20bb05 ever since; the three commits after it never shipped.

Author: reddy-sh

amplify/functions/api/store.ts

@@ -32,6 +32,7 @@ import {
     GetCommand,
     PutCommand,
     QueryCommand,
+    ScanCommand,
     UpdateCommand
 } from '@aws-sdk/lib-dynamodb';