Phase 3C: Deployment pipeline & Store-and-Forward engine

Deployment Manager (WP-1–8, WP-16):
- DeploymentService: full pipeline (flatten→validate→send→track→audit)
- OperationLockManager: per-instance concurrency control
- StateTransitionValidator: Enabled/Disabled/NotDeployed transition matrix
- ArtifactDeploymentService: broadcast to all sites with per-site results
- Deployment identity (GUID + revision hash), idempotency, staleness detection
- Instance lifecycle commands (disable/enable/delete) with deduplication

Store-and-Forward (WP-9–15):
- StoreAndForwardStorage: SQLite persistence, 3 categories, no max buffer
- StoreAndForwardService: fixed-interval retry, transient-only buffering, parking
- ReplicationService: async best-effort to standby (fire-and-forget)
- Parked message management (query/retry/discard from central)
- Messages survive instance deletion, S&F drains on disable

620 tests pass (+79 new), zero warnings.

src/ScadaLink.Commons/Types/Enums/InstanceState.cs

@@ -2,6 +2,7 @@ namespace ScadaLink.Commons.Types.Enums;
 
 public enum InstanceState
 {
+    NotDeployed,
     Enabled,
     Disabled
 }

src/ScadaLink.Commons/Types/Enums/StoreAndForwardCategory.cs

@@ -0,0 +1,11 @@
+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// WP-9: Categories for store-and-forward messages.
+/// </summary>
+public enum StoreAndForwardCategory
+{
+    ExternalSystem,
+    Notification,
+    CachedDbWrite
+}

src/ScadaLink.Commons/Types/Enums/StoreAndForwardMessageStatus.cs

@@ -0,0 +1,12 @@
+namespace ScadaLink.Commons.Types.Enums;
+
+/// <summary>
+/// WP-9: Status of a store-and-forward message.
+/// </summary>
+public enum StoreAndForwardMessageStatus
+{
+    Pending,
+    InFlight,
+    Parked,
+    Delivered
+}