feat: Add region validation for cross-region deployment

Author: newman911

modules/sagemaker/sagemaker-templates/templates/model_deploy/seed_code/deploy_app/app.py

@@ -5,6 +5,18 @@
 from deploy_app.pipeline_stack import PipelineStack
 
 app = cdk.App()
+
+# All deployment regions must match - cross-region endpoint deployment is not supported
+# because model packages contain region-specific container image URIs
+regions = {
+    "dev": constants.DEV_REGION,
+    "pre-prod": constants.PRE_PROD_REGION,
+    "prod": constants.PROD_REGION,
+}
+mismatched = {k: v for k, v in regions.items() if v != constants.DEV_REGION}
+if mismatched:
+    raise ValueError(f"All deployment regions must match dev region ({constants.DEV_REGION}). Mismatched: {mismatched}")
+
 PipelineStack(
     app,
     f"{constants.PROJECT_NAME}-pipeline",