docs: update backlog

.github/instructions/BACKLOG.md

@@ -21,7 +21,7 @@ Status reflects 2026-08-06 code scan + implementation batches.
 - [x] Implement WebSocket chat backend (Go) with room fan-out
 - [x] Implement private DM channel routing
 - [x] Implement Redis presence tracking for chat
-- [ ] Implement Redis pub/sub for multi-instance chat
+- [x] Implement Redis pub/sub for multi-instance chat
 - [x] Implement Redis rate limiting (INCR + EXPIRE windowing, >10/10s throttle)
 - [x] Implement chat message persistence (SQLite v1, PostgreSQL migration path)
 - [x] Implement moderation commands (/mod, /mute, /ban) in backend
@@ -119,8 +119,8 @@ Status reflects 2026-08-06 code scan + implementation batches.
 ## Documentation
 
 - [x] Document API contracts in API.md
-- [ ] Document deployment runbook in DEPLOYMENT.md
-- [ ] Document monitoring setup in MONITORING.md
-- [ ] Document security model in SECURITY.md
+- [x] Document deployment runbook in DEPLOYMENT.md
+- [x] Document monitoring setup in MONITORING.md
+- [x] Document security model in SECURITY.md
 - [x] Create incident runbook (docs/incident-runbook.md)
-- [ ] Write Level 2/3 building block views
+- [x] Write Level 2/3 building block views