Shorten multi-attachment workflow stack name to avoid length limits

Change stack name from 'thingpress-integration-test-multi-{run_number}' to
'tp-int-multi-{run_number}' to prevent IAM role and resource name length
limit errors during CloudFormation stack creation.

Stack name now: tp-int-multi-{run_number} (e.g., tp-int-multi-123)

Author: rpcme

.github/workflows/integration-tests-multi.yml

@@ -28,7 +28,7 @@ jobs:
 
     env:
       AWS_REGION: ${{ github.event.inputs.region || secrets.AWS_REGION || 'us-east-1' }}
-      STACK_NAME: thingpress-integration-test-multi-${{ github.run_number }}
+      STACK_NAME: tp-int-multi-${{ github.run_number }}
 
     steps:
       - name: Checkout code