fix(high-severity): close 9 of 10 open High findings across 8 modules

Comm-016: delete dead HandleConnectionStateChanged + _debugSubscriptions /
_inProgressDeployments tracking + ConnectionStateChanged message record.
Disconnect detection is owned by the transport layers (gRPC keepalive PING
~25s; Ask-timeout at CommunicationService). Updates the
Component-Communication.md design doc to make that explicit.

SnF-018: NotificationForwarder.DeliverAsync now discards a corrupt buffered
payload (Warning log + return true) instead of returning false and parking
the row — honoring the design's "notifications do not park" invariant.

DM-018: reconciliation no longer force-sets Enabled, preserving an
intentional Disabled state after central failover.

ESG-018: DeliverBufferedAsync (both ExternalSystemClient + DatabaseGateway)
catches JsonException and returns false, turning a corrupt buffered row
into a parked operation instead of a retry-forever poison message.

InboundAPI-022: register ActiveNodeGate as IActiveNodeGate in the Central
DI branch so standby-node gating is actually wired up in production.

NS-019: remove orphaned NotificationDeliveryService /
INotificationDeliveryService / NotificationResult; central notification
delivery now lives entirely in NotificationOutbox.

SEL-016: normalise From/To filters to UTC before ISO-string compare so
non-UTC DateTimeOffset clients no longer get spuriously excluded events.

TE-017: include Description on attributes/alarms and a HashableConnections
projection (protocol, endpoint JSON, failover count) in the revision hash
and DiffService; staleness detection now catches description-only and
connection-endpoint edits.

Transport-001 and Transport-002 (also High) remain Open — they're being
handled in a follow-up batch because both touch BundleImporter.cs and
must serialise.

src/ScadaLink.NotificationService/NotificationOptions.cs

@@ -5,10 +5,10 @@ namespace ScadaLink.NotificationService;
 /// <c>ScadaLink:Notification</c> configuration section.
 ///
 /// SMTP settings are primarily carried by the deployed <c>SmtpConfiguration</c>
-/// entity. NS-017: these values are the fallback used by
-/// <see cref="NotificationDeliveryService"/> when the corresponding
-/// <c>SmtpConfiguration</c> field is left unset (non-positive) on a partially
-/// deployed row — a value present on the row always takes precedence.
+/// entity. NS-017: these values are the fallback used by the central
+/// Notification Outbox's <c>EmailNotificationDeliveryAdapter</c> when the
+/// corresponding <c>SmtpConfiguration</c> field is left unset (non-positive) on a
+/// partially deployed row — a value present on the row always takes precedence.
 /// </summary>
 public class NotificationOptions
 {