Spike: Postgres → ClickHouse CDC

[khvn26]

Goal

To run the membership feature self-hosted with ClickHouse as the warehouse, we need a Postgres → ClickHouse CDC pipeline. Compare:

• Debezium + Kafka Connect — battle-tested, heavy.
• PeerDB — Postgres-native, lighter operational footprint.
• Materialize / Flink — overkill but worth quantifying.
• Custom logical-replication consumer — minimal deps, more code.

Output

• A user-facing docs PR including a written tradeoff comparison and a rough cost/maintenance budget for self-hosted customers.
• An issue or epic scoping work for the chosen implementation.