Apply Codex review findings across all 17 components

Template Engine: add composed member addressing (path-qualified canonical names),
override granularity per entity type, semantic validation (call targets, arg types),
graph acyclicity enforcement, revision hashes for flattened configs.

Deployment Manager: add deployment ID + idempotency, per-instance operation lock
covering all mutating commands, state transition matrix, site-side apply atomicity
(all-or-nothing), artifact version compatibility policy.

Site Runtime: add script trust model (forbidden APIs, execution timeout, constrained
compilation), concurrency/serialization rules (Instance Actor serializes mutations),
site-wide stream backpressure (per-subscriber buffering, fire-and-forget publish).

Communication: add application-level correlation IDs for protocol safety beyond
Akka.NET transport guarantees.

External System Gateway: add 408/429 as transient errors, CachedCall idempotency
note, dedicated dispatcher for blocking I/O isolation.

Health Monitoring: add monotonic sequence numbers to prevent stale report overwrites.

Security: require LDAPS/StartTLS for LDAP connections.

Central UI: add failover behavior (SignalR reconnect, JWT survives, shared Data
Protection keys, load balancer readiness).

Cluster Infrastructure: add down-if-alone=on for safe singleton ownership.

Site Event Logging: clarify active-node-only logging (no replication), add 1GB
storage cap with oldest-first purge.

Host: add readiness gating (health check endpoint, no traffic until operational).

Commons: add message contract versioning policy (additive-only evolution).

Configuration Database: add optimistic concurrency on deployment status records.

Component-Security.md

@@ -18,6 +18,7 @@ Central cluster. Sites do not have user-facing interfaces and do not perform ind
 ## Authentication
 
 - **Mechanism**: The Central UI presents a username/password login form. The app validates credentials by binding to the LDAP/AD server with the provided credentials, then queries the user's group memberships.
+- **Transport security**: LDAP connections **must** use LDAPS (port 636) or StartTLS to encrypt credentials in transit. Unencrypted LDAP (port 389) is not permitted.
 - **No local user store**: All identity and group information comes from AD. No credentials are cached locally.
 - **No Windows Integrated Authentication**: The app authenticates directly against LDAP/AD, not via Kerberos/NTLM.