docs: integrate RDS and ACK architecture memory

.project-docs/10-decisions/decision-index.md

@@ -4,6 +4,9 @@
 
 | ID | Decision | Status | Date | Applies To | Detail |
 |---|---|---|---|---|---|
+| RDS-001 | Production persistence uses explicit direct PostgreSQL through one server-only adapter; local JSON is explicit development/test mode. | Accepted | 2026-08-12 | Server stores and scripts | `ZHINIAN_DATA_BACKEND=postgres` fails closed and never silently falls back. |
+| RDS-002 | Database changes use versioned, checksummed, advisory-locked migrations executed by a one-shot deployment Job. | Accepted | 2026-08-12 | Database schema and ACK rollout | Migrations do not run in each Web pod init container. |
+| ACK-001 | Worker remains an HTTP poller and does not receive RDS credentials; Web owns database access. | Accepted | 2026-08-12 | ACK workloads | Worker calls the internal Web Service with a shared internal token. |
 
 ## Superseded Decisions