Add Airflow 3.1.7 compatibility testing

[judoole]

Important

As a contributor validating Airflow compatibility
I want to run the suite against Airflow 2.10.5 and Airflow 3.1.7 from easy local targets and CI
So that I can catch major-version regressions without rebuilding the setup by hand each time

Feature: Airflow version compatibility testing

  Scenario: Run the compatibility suite against Airflow 2.10.5
    Given a prepared Airflow 2.10.5 environment
    When I run the Airflow 2 compatibility lane
    Then the CI subset of the test suite passes

  Scenario: Run the compatibility suite against Airflow 3.1.7
    Given a prepared Airflow 3.1.7 environment
    When I run the Airflow 3 compatibility lane
    Then the CI subset of the test suite passes

  Scenario: Reuse versioned local environments
    Given versioned Airflow venvs already exist locally
    When I run the versioned local test targets again
    Then the existing environments are reused instead of rebuilding from scratch

References

• CI matrix: .github/workflows/ci.yml
• Local targets: Makefile
• Compatibility layer: src/airflow_bdd/compat.py