Release: GitHub Actions upgrades, SQLAlchemy pooling, and SD-8383 dataset collaborators

[MarkCalvert]

Summary

• GitHub Actions upgrades: Bumped all workflow action versions (actions/checkout v4→v6, docker/login-action v3→v4, docker/metadata-action v5→v6, docker/build-push-action v5→v7, aquasecurity/trivy-action 0.26.0→0.35.0, github/codeql-action/upload-sarif v3→v4). Added TRIVY_DB_REPOSITORY env var pointing to the ECR mirror to resolve Trivy DB pull failures.
• Dependabot: Added .github/dependabot.yml to track GitHub Actions dependency updates weekly.
• CKAN worker base image build: Updated .ahoy.yml to explicitly build the CKAN base image before the worker image so the worker Dockerfile can use it as its base.
• SD-8383 Dataset collaborators: Enabled ckan.auth.allow_dataset_collaborators = true in dbca.ini.
• SQLAlchemy connection pooling: Added pool tuning settings (pool_pre_ping, pool_recycle = 1800, pool_size = 10, max_overflow = 20, pool_timeout = 30) to prevent stale connection failures.

Related

• Extension changes: Release: ORM rollback middleware and collection notice sidebar ckanext-dbca#22
• SD-8383