Summary

• Build a separate zeph-db nextest archive in build-tests with --no-default-features --features test-utils (postgres backend + testcontainers)
• Download and run this archive in the integration job alongside existing testcontainer tests
• No recompilation in integration — archive is built with sccache in build-tests

Test plan

• CI Integration Tests job runs both existing and new postgres tests
• migrations_apply_cleanly, migrations_are_idempotent, basic_insert_select_delete, fts_trigger_and_search pass with Docker-backed PostgreSQL
• Overall workflow duration not significantly increased (postgres build is incremental via sccache)