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-HealthMonitoring.md

@@ -34,7 +34,7 @@ Site clusters (metric collection and reporting). Central cluster (aggregation an
 ## Reporting Protocol
 
 - Sites send a **health report message** to central at a configurable interval (default: **30 seconds**).
-- Each report is a **flat snapshot** containing the current values of all monitored metrics. Central replaces the entire previous state for that site on receipt.
+- Each report is a **flat snapshot** containing the current values of all monitored metrics, a **monotonic sequence number**, and the **report timestamp** from the site. Central replaces the previous state for that site only if the incoming sequence number is higher than the last received — this prevents stale reports (e.g., delayed in transit or from a pre-failover node) from overwriting newer state.
 - **Offline detection**: If central does not receive a report within a configurable timeout window (default: **60 seconds** — 2x the report interval), the site is marked as **offline**. This gives one missed report as grace before marking offline.
 - **Online recovery**: When central receives a health report from a site that was marked offline, the site is automatically marked **online**. No manual acknowledgment required — the metrics in the report provide immediate visibility into the site's condition.