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.

tests/ScadaLink.StoreAndForward.Tests/StoreAndForwardOptionsTests.cs

@@ -0,0 +1,37 @@
+namespace ScadaLink.StoreAndForward.Tests;
+
+/// <summary>
+/// WP-9: Tests for StoreAndForwardOptions defaults and configuration.
+/// </summary>
+public class StoreAndForwardOptionsTests
+{
+    [Fact]
+    public void DefaultOptions_HasReasonableDefaults()
+    {
+        var options = new StoreAndForwardOptions();
+
+        Assert.Equal("./data/store-and-forward.db", options.SqliteDbPath);
+        Assert.True(options.ReplicationEnabled);
+        Assert.Equal(TimeSpan.FromSeconds(30), options.DefaultRetryInterval);
+        Assert.Equal(50, options.DefaultMaxRetries);
+        Assert.Equal(TimeSpan.FromSeconds(10), options.RetryTimerInterval);
+    }
+
+    [Fact]
+    public void Options_CanBeCustomized()
+    {
+        var options = new StoreAndForwardOptions
+        {
+            SqliteDbPath = "/custom/path.db",
+            ReplicationEnabled = false,
+            DefaultRetryInterval = TimeSpan.FromMinutes(5),
+            DefaultMaxRetries = 100,
+            RetryTimerInterval = TimeSpan.FromSeconds(30)
+        };
+
+        Assert.Equal("/custom/path.db", options.SqliteDbPath);
+        Assert.False(options.ReplicationEnabled);
+        Assert.Equal(TimeSpan.FromMinutes(5), options.DefaultRetryInterval);
+        Assert.Equal(100, options.DefaultMaxRetries);
+    }
+}