Airflow DAG integration tests beyond import #52

Background

Identified during OSS audit v2 of startupintel.

Problem Statement

DAG tasks not invoked.

Proposed Solution

Task callable tests.

Acceptance Criteria

• Implementation complete
• Tests pass
• Documented in README or docs/

Files / Modules Affected

tests/test_airflow/

Suggested labels: priority:low, difficulty:intermediate, category:testing
Milestone: v2.0-features
OSS Audit: Master Backlog v2