fix: configure filtered Debezium publications

[vpol]

What changed

• adds a database-backed Debezium heartbeat model and migration
• creates explicit filtered API and ClickHouse publications with publish_generated_columns = stored
• disables connector-side publication autocreation and points both connectors at the new publications
• excludes post.views so view-only updates can be skipped, and excludes generated post.slug
• executes heartbeat upserts and filters heartbeat row events from the application SMT pipeline

Why

After the separate publication rollout, PostgreSQL 18 rejected updates to post with Replica identity must not contain unpublished generated columns. The table uses REPLICA IDENTITY FULL and slug is a stored generated column, while connector-created publications do not enable generated-column publishing.

The publications are now migration-owned so they can explicitly publish stored generated columns. Publication setup includes only configured tables that exist, which handles removed legacy tables such as user_state.

Validation

• complete 538-migration chain against PostgreSQL 18
• publication metadata verified with pubgencols = stored
• UPDATE post SET views = views WHERE false succeeds without SQLSTATE 42P10
• heartbeat upsert succeeds
• filtered-publication migration revert and reapply
• pnpm run build
• pnpm run lint
• git diff --check