1a454f76cf
Add api/cdc_consumer.py: aiokafka background consumer subscribes to the CDC topics (postgres_sales/mysql_hr/mongodb_supplychain + cassandra/neo4j), parses Debezium before/after envelopes, keeps a ring buffer and publishes each change live as type=cdc_change. Endpoints /api/changes, /api/changes/stats, /status.