Post-Migration Data Integrity Validation Framework

Act as a Data Quality Assurance Lead. Create an uncompromising, fully automated post-migration data validation suite. This Python/Bash framework must execute in a blocking state immediately after a CI/CD database migration script completes, but strictly *before* the global load balancer is allowed to switch application traffic to the new version. The script must programmatically query and mathematically compare the [SOURCE_SCHEMA] against the new [TARGET_SCHEMA], evaluating exact row counts, generating MD5 hash checksums on highly critical columns (like balances or passwords), and executing complex [VALIDATION_LOGIC] (e.g., ensuring zero nulls were introduced during a type cast). If any mathematical parity validation fails, the script must return a non-zero exit code to the CI runner, instantly aborting the release and triggering an idempotent database rollback.