feat(infra): Aurora prod backup retention 14d + window; prod-only CDK context

Bump Aurora automated-backup (PITR) retention 7->14d and set a preferred backup
window for the prod tenant. Dedicated AWS Backup vault + cross-account restore
test is a tracked follow-up (no org central-backup design exists yet). Prune the
stale mgmt-account AZ context; prod (011934824531) is the only deploy target.

infra/cdk.context.json

@@ -1,5 +1,5 @@
 {
-  "availability-zones:account=328440206208:region=us-east-1": [
+  "availability-zones:account=011934824531:region=us-east-1": [
     "us-east-1a",
     "us-east-1b",
     "us-east-1c",

infra/deploy-role/permissions-policy.json

@@ -16,7 +16,12 @@
             "Sid": "CdkDeployHealthCheck",
             "Effect": "Allow",
             "Action": "cloudformation:DescribeStacks",
-            "Resource": "*"
+            "Resource": "*",
+            "Condition": {
+                "StringEquals": {
+                    "aws:RequestedRegion": "us-east-1"
+                }
+            }
         },
         {
             "Sid": "FrontendSiteBucketSync",

infra/lib/foundation-stack.ts

@@ -105,7 +105,10 @@ export class FoundationStack extends cdk.Stack {
       serverlessV2MaxCapacity: 4,
       enableDataApi: true,
       storageEncrypted: true,
-      backup: { retention: cdk.Duration.days(7) },
+      // Aurora native automated backups (PITR). 14-day retention for the prod tenant;
+      // a dedicated AWS Backup vault + cross-account restore test is a tracked follow-up
+      // (no org central-backup design exists yet — see the prod-deploy plan Phase 4 fallback).
+      backup: { retention: cdk.Duration.days(14), preferredWindow: '07:00-08:00' },
       deletionProtection: config.retainData,
       removalPolicy: config.retainData ? cdk.RemovalPolicy.RETAIN : cdk.RemovalPolicy.DESTROY,
       defaultDatabaseName: 'proposals',