Fail test_run_math_pipeline_e2e fast when DynamoDB is unavailable

Add require_dynamodb() guard to the dynamodb_resource fixture so it
fails in ~3s instead of hanging on a TCP connection to stopped DynamoDB.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jucor

delphi/tests/test_math_pipeline_runs_e2e.py

@@ -32,6 +32,9 @@
 @pytest.fixture(scope="module")
 def dynamodb_resource():
     """Create a resource connection to the test DynamoDB."""
+    from tests.conftest import require_dynamodb
+    require_dynamodb()
+
     endpoint_url = os.environ.get('DYNAMODB_ENDPOINT', 'http://localhost:8000')
     if not endpoint_url:
         pytest.fail("DYNAMODB_ENDPOINT not set. Cannot connect to test DynamoDB.")